Different Degrees Of Asymmetry Research Articles

Engineering quasi-bound states in the continuum in asymmetric waveguide gratings

Abstract The occurrence of quasi-bound states in the continuum (qBIC) in all-dielectric asymmetric grating waveguide couplers with different degrees of asymmetry under normal light incidence is analysed from the viewpoint of identifying the most promising configuration for realizing the highest quality (Q) factor under the condition of utmost efficiency (i.e. total extinction). Considering asymmetric gratings produced by altering every Nth ridge of a conventional (symmetric) grating coupler, we analyse different regimes corresponding to the interplay between diffractive coupling to waveguide modes and band gap effects caused by the Bragg reflection of waveguide modes. The symmetric and double- and triple-period asymmetric grating couplers are considered in detail for the same unperturbed two-mode waveguide and the grating coupler parameters that ensure the occurrence of total transmission extinction at the same wavelengths. It is found that the highest Q is expected for the double-period asymmetric grating, a feature that we explain by the circumstance that the first-order distributed Bragg resonator (DBR) is realized for this configuration while, for other configurations, the second-order DBR comes into play. Experiments conducted at telecom wavelengths for all three cases using thin-film Al2O3-on-MgF2 waveguides and Ge diffraction gratings exhibit the transmission spectra in qualitative agreement with numerical simulations. Since the occurrence of considered qBIC can be analytically predicted, the results obtained may serve as reliable guidelines for intelligent engineering of asymmetric grating waveguide couplers enabling highly resonant, linear and nonlinear, electromagnetic interactions.

Asymmetric structures to switch on the selective oxygen reduction to hydrogen peroxide

Carbon defects coupled with heteroatoms can asymmetrically rearrange the local electronic distribution and coordination environment of active sites, improving the catalytic selectivity and activity of a two-electron oxygen reduction reaction (2eORR). In this study, an asymmetry defective carbon (asy-DC) structure using wolfberry as the carbon source is employed to adjust the charge distribution of active sites with different degrees of asymmetry caused by N→S coordination bonds. The asymmetric region exhibits a considerable positive correlation between the asymmetry degree and adsorption energy for OOH*, presenting a volcano relation between the asymmetry degree and catalytic activity. The optimised asy-DC catalyst exhibits high selectivity and reliable activity after 12 h of stability testing. This study can provide a new reference into the origin of ORR activity and selectivity.

The effect of the colour red in 20 years of Olympic taekwondo

The objectives of this study were (1) to analyse the relationship between the colour of the protectors and the outcome of 895 matches in the six Olympic Games in which taekwondo has been included, and (2) to analyse the effect of confounding factors through the different degrees of asymmetry between contestants. Data were recorded on the colour of each athlete’s protectors, the scoring system, the sex of the athlete, the weight category, the round of competition, the winner of the match, the method of victory and the points scored by each athlete. Among the main results, a relationship emerged between male athletes wearing red and winning the match (p = 0.034) under the manual scoring system. There were relationships between female athletes wearing blue and winning the match in the quarterfinal (p = 0.014) and last 16 rounds (p = 0.021) using the manual and electronic scoring systems respectively. In female athletes, relationships emerged between wearing blue and winning the match with small (p = 0.008) and medium (p = 0.047) asymmetry under the manual system and with large (p = 0.036) asymmetry under the electronic system. The electronic system had a positive impact on the fairness of Olympic competition. Red tends to gain in importance as the asymmetry between the two athletes decreases, but not enough to give a competitive advantage. The results for Olympic competition held in the now concluded era of the manual system confirmed the presence of the colour effect as a result of psychological factors attributable to referees and judges.

Trigeminal Stimulation and Visuospatial Performance: The Struggle between Chewing and Trigeminal Asymmetries.

Chewing improves visuospatial performance through locus coeruleus (LC) activation. The effects of bilateral and unilateral mastication were investigated in subjects showing different degrees of asymmetry in masseter electromyographic (EMG) activity during clenching and in pupil size at rest (anisocoria), which is a proxy of LC imbalance. Correlations between performance changes and asymmetry values were found in males, but not in females. Among males, subjects with low asymmetry values (balanced-BAL) were more sensitive than those with high asymmetry values (imbalanced-IMB) to bilateral and unilateral chewing on the side with higher EMG activity (hypertonic). The opposite was true for hypotonic side chewing. BAL subjects were sensitive to unilateral chewing on both sides, while in IMB subjects, hypertonic side chewing did not influence performance in either males or females. Bilateral chewing elicited larger effects in BAL subjects than in IMB subjects, exceeding the values predicted from unilateral chewing in both groups. Finally, pupil size and anisocoria changes elicited by chewing were correlated with asymmetry values, independent of sex. Data confirmed the facilitation of visuospatial performance exerted by chewing. Trigeminal asymmetries modulate the chewing effects, making occlusal rebalancing an appropriate strategy to improve performance.

Exploring the photovoltaic properties of promising non-fullerene acceptors with different degrees of asymmetry due to halogenations of terminal groups

Over the past few years, the strategy of asymmetric modification has become popular for designing new photovoltaic materials because it can effectively improve optoelectronic performance and morphology, therefore power conversion efficiency (PCE). However, how the halogenations (to further change asymmetry) of terminal groups (TGs) of an asymmetric small-molecule non-fullerene acceptor (Asy-SM-NFA) influence optoelectronic properties is still not very clear. In this work, we have selected a promising Asy-SM-NFA IDTBF (the OSC based on it has a PCE of 10.43 %), exacerbated the asymmetry through fluorinations of TGs, and finally designed six new molecules. Based on density functional theory (DFT) and time-dependent DFT calculations, we systematically examine how the changed asymmetry impacts the optoelectronic properties. We find that the halogenations of TGs may significantly affect the molecular planarity, dipole moment, electrostatic potential, exciton binding energy, energy loss, and absorption spectrum. And the results show that newly designed BR-F1 and IM-mF (m = 1,3, and 4) are potential Asy-SM-NFAs because they all have enhanced absorption spectra in the visible region. Therefore, we provide a meaningful direction for the design of asymmetric NFA.

Understanding the diurnal cycle of land–atmosphere interactions from flux site observations

Abstract. Land–atmosphere interactions have been investigated at daily or longer timescales due to limited data availability and large errors for measuring high-frequency variations. Yet coupling at the subdaily timescale is characterized by the diurnal cycle of incoming solar radiation and surface fluxes. Based on flux tower observations, this study investigates the climatology of observed land–atmosphere interactions on subdaily timescales during the warm season. Process-based multivariate metrics are employed to quantitatively measure segmented coupling processes, and mixing diagrams are adopted to demonstrate the integrative moist and thermal energy budget evolution in the atmospheric mixed layer. The land, atmosphere, and combined couplings for the entire daily mean, midday, and midnight periods show different situations to which surface latent and sensible heat fluxes are relevant, and they also reveal the climate sensitivity to soil moisture and surface air temperature. The 24 h coevolution of the moist and thermal energy within the boundary layer traces a particular path on mixing diagrams, exhibiting different degrees of asymmetry (time shifts) in water- and energy-limited locations. Water- and energy-limited processes also show opposing long tails of low humidity during the daytime and nighttime, related to the impact on land and atmospheric couplings of latent heat flux and other diabatic processes like radiative cooling. This study illustrates the necessity of considering the entire diurnal cycle to understand land–atmosphere coupling processes comprehensively in observations and models.

The Role of Art Expertise and Symmetry on Facial Aesthetic Preferences

Humans, like other species, have a preference for symmetrical visual stimuli, a preference that is influenced by factors such as age, sex, and artistic training. In particular, artistic training seems to decrease the rejection of asymmetry in abstract stimuli. However, it is not known whether the same trend would be observed in relation to concrete stimuli such as human faces. In this article, we investigated the role of expertise in visual arts, music, and dance, in the perceived beauty and attractiveness of human faces with different asymmetries. With this objective, the beauty and attractiveness of 100 photographs of faces with different degrees of asymmetry were evaluated by 116 participants with different levels of art expertise. Expertise in visual arts and dance was associated with the extent to which facial asymmetry influenced the beauty ratings assigned to the faces. The greater the art expertise in visual arts and dance, the more indifferent to facial asymmetry the participant was to evaluate beauty. The same effect was not found for music and neither for attractiveness ratings. These findings are important to help understand how face aesthetic evaluation is modified by artistic training and the difference between beauty and attractiveness evaluations.

Controlled Asymmetric Charge Distribution of Active Centers in Conjugated Polymers for Oxygen Reduction.

Active center reconstruction is essential for high performance oxygen reduction reaction (ORR) electrocatalysts. Usually, the ORR activity stems from the electronic environment of active sites by charge redistribution. We introduce an asymmetry strategy to adjust the charge distribution of active centers by designing conjugated polymer (CP) catalysts with different degrees of asymmetry. We synthesized asymmetric backbone CP (asy-PB) by modifying B←N coordination bonds and asymmetric sidechain CP (asy-PB-A) with different alkyl chain lengths. Both CPs with backbone and sidechain asymmetry exhibit superior ORR performance to their symmetric counterparts (sy-P and sy-PB). The asy-PB with greater asymmetry shows higher catalytic activity than asy-PB-A with relatively smaller asymmetry. DFT calculations reveal that the increased dipole moment and non-uniform charge distribution caused by asymmetric structure endows the center carbon atom of bipyridine with efficient catalytic activity.

Controlled Asymmetric Charge Distribution of Active Centers in Conjugated Polymers for Oxygen Reduction

AbstractActive center reconstruction is essential for high performance oxygen reduction reaction (ORR) electrocatalysts. Usually, the ORR activity stems from the electronic environment of active sites by charge redistribution. We introduce an asymmetry strategy to adjust the charge distribution of active centers by designing conjugated polymer (CP) catalysts with different degrees of asymmetry. We synthesized asymmetric backbone CP (asy‐PB) by modifying B←N coordination bonds and asymmetric sidechain CP (asy‐PB‐A) with different alkyl chain lengths. Both CPs with backbone and sidechain asymmetry exhibit superior ORR performance to their symmetric counterparts (sy‐P and sy‐PB). The asy‐PB with greater asymmetry shows higher catalytic activity than asy‐PB‐A with relatively smaller asymmetry. DFT calculations reveal that the increased dipole moment and non‐uniform charge distribution caused by asymmetric structure endows the center carbon atom of bipyridine with efficient catalytic activity.

Interfacial flow of a surfactant-laden interface under asymmetric shear flow

HypothesisThe shear stress of the axisymmetric flow field triggers a nonuniform distribution of the surfactants at the surface of a rising bubble, known as stagnant cap. The formation of the stagnant cap gives rise to Marangoni stresses that reduce the mobility of the interface, which in return reduces the rising velocity. However, the conditions in technological processes usually deviate from the linear rise of a single bubble in a quiescent unbounded liquid. Asymmetric shear can act on the bubble surface e.g. due to the vorticity in the surrounding flow, bubble–bubble interactions, or influence of the reactor wall. A different surfactant distribution at the interface is expected under asymmetric shear, which can change the hydrodynamic behavior of the interface drastically. ExperimentsHere we conduct model experiments with a bubble or a drop at the tip of a capillary placed in a defined flow field. Thereby we investigate the influence of asymmetric shear forces on the interface in the presence of surfactants. Microscopic particle tracking velocimetry is employed to measure the velocity of the surfactant-laden interface for different degrees of asymmetry in the surrounding liquid flow. FindingsWe show a direct experimental observation of the circulating flow at the interface under asymmetric shear, which prevents the formation of the typical stagnant cap. Additionally, we reveal that the interface remains mobile regardless of the surfactant concentration. Our results confirm that increasing the degree of asymmetry increases the shear forces and thus the interfacial velocity.

Fine structure of bright and dark excitons in asymmetric droplet epitaxy GaAs/AlGaAs quantum dots

We have calculated the exciton fine structure splittings (FSS) of asymmetric GaAs/AlGaAs quantum dots (QDs) obtained after Al droplet epitaxy and subsequent nanoholes formation followed by annealing and GaAs filling of nanoholes. We used a $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ model and considered the heavy-hole and light-hole mixing to calculate the electron-hole exchange interaction (EI). The two components, long-range (LR) and short-range (SR) of the EI, were deduced. The exciton fine structure is organized, as usual in zinc-blende compounds, into two groups of states: bright (optically active) and dark states. The bright-dark and bright-bright splittings contain LR and SR contributions, the LR part representing 5 to 68% of the total bright-dark splitting and 69 to 76% of the total bright-bright splitting for sizes experimentally explored. In QDs having ${\mathrm{C}}_{2v}$ symmetry, LR and SR contributions to dark-dark splitting have to be calculated at the second order of perturbation theory. A good agreement between the theory and experiment is obtained for QDs with different degrees of asymmetry, from QD having an isotropic shape to QD with a very anisotropic shape.

Multiple Fano resonances with flexible tunablity based on symmetry-breaking resonators

A symmetry-breaking nanostructure is proposed to achieve multiple Fano resonances. The nanostructure consists of an asymmetric ring resonator coupled to a plasmonic waveguide. The broken symmetry is introduced by deviating the centers of regular ring. New resonant modes that are not accessible through a regular symmetric ring cavity are excited. Thus, one asymmetric cavity can provide more than one resonant mode with the same mode order. As a result, the interval of Fano resonances is greatly reduced. By combining different rings with different degrees of asymmetry, multiple Fano resonances are generated. Those Fano resonances have different dependences on structural parameters due to their different physical origin. The resonance frequency and resonance peak number can be arbitrarily adjusted by changing the degree of asymmetry. This research may provide new opportunities to design on-chip optical devices with great tuning performance.

Effect of Clearances in Mill Stands on Strip End Motion During Finishing Rolling

The process stability of finishing mill is significantly influenced by the clearance between the chocks and housing in mill stands. The on-site data of a finishing mill had shown that the clearances in the finishing mill stands were clearly associated with the incidence of strip end flip. The aim of this work was to establish a numerical model to analyze the effect of the clearances on the deviation of the centerline of the strip and on the incidence of strip end flip. By adopting conditions from a particular strip, the numerical model not only predicted the strip end shape, but also visualized strip end flip, which would be otherwise invisible. Four different degrees of asymmetry regarding work rolls and backup rolls were postulated. It was found that the degradation of the work rolls’ clearance level was the most significant influence on the centerline deviation of the strip. Strip end flip was most susceptible to the degradation of the horizontal clearance of the work roll. The simultaneous degradation of the work rolls’ and backup rolls’ level of clearance led to larger reactions and enhanced the asymmetric wear on the liners. The superimposed axial clearances at the roll end provided an axial constraint to the work roll, and were able to reverse the trend of centerline deviation. The numerical results provided a guideline for designing a suitable maintenance strategy for clearances.

Time series irreversibility analysis using Jensen–Shannon divergence calculated by permutation pattern

An important feature of the time series in the real world is that its distribution has different degrees of asymmetry, which is what we call irreversibility. In this paper, we propose a new method named permutation pattern (PP) to calculate the Kullback–Leibler divergence ( $${D}_{\mathrm{KL}}$$ ) and the Jensen–Shannon divergence ( $${D}_{\mathrm{JS}}$$ ) to explore the irreversibility of time series. Meanwhile, we improve $${D}_{\mathrm{JS}}$$ and obtain a complete mean divergence ( $${D}_{\mathrm{m}}$$ ) through averaging $${D}_{\mathrm{KL}}$$ of a time series and its inverse time series. The variation trend of $${D}_{\mathrm{m}}$$ is similar to $${D}_{\mathrm{JS}}$$ , but the value of $${D}_{\mathrm{m}}$$ is slightly larger and the description of irreversibility is more intuitive. Furthermore, we compare $${D}_{\mathrm{JS}}$$ and $${D}_{\mathrm{m}}$$ calculated by PP with those calculated by the horizontal visibility graph, and discuss their respective characteristics. Then, we investigate the advantages of $$\mathrm{D}_{\mathrm{JS}}$$ and $${D}_{\mathrm{m}}$$ through length variation, dynamic time variation, multiscale and so on. It is worth mentioning that we introduce Score and variance to analyze the practical significance of stock irreversibility.

Effect of the temporal laser pulse asymmetry on pair production processes during intense laser-electron scattering

We investigate the effects of laser pulse shape on strong-field quantum electrodynamics (QED) processes during the collision between a relativistic electron beam and an intense laser pulse. The interplay between high-energy photon emission and two pair production processes, i.e. nonlinear Breit–Wheeler (BW) and Trident, was investigated using particle-in-cell simulations. We found that the temporal evolution of these two processes could be controlled by using laser pulses with different degrees of asymmetry. The temporal envelope of the laser pulse can significantly affect the number of pairs coming from the Trident process, while the nonlinear BW process is less sensitive to it. This study shows that the two QED processes can be examined with state-of-the-art petawatt lasers and the discrimination of the two pair creation processes is feasible by adjusting the temporal asymmetry of the colliding laser pulse.

Equivalent Circuits for Nonsymmetric Reciprocal Two Ports Based on Eigenstate Formulation

Equivalent circuit topologies for two-port reciprocal nonsymmetric structures are proposed as an extension of the well-known symmetric lattice network. An eigenstate formulation approach that allows the separation of the eigenmodes in the equivalent circuit, as in the symmetric lattice network, is adopted. Four topologies based on series or parallel immittances with the combined use of some transformers are proposed. Particular cases, such as symmetric networks and parallel and series single elements, are derived from the proposed topologies. Moreover, power dissipation in these topologies is also analyzed. A modification in the reference planes is further introduced to achieve power dissipation orthogonality in the two branches of the circuit, as happens in the symmetric lattice network. Additionally, real transformation ratios for the transformers and nonnegative real parts for the immittances are obtained. Finally, the equivalent circuit is extracted for a complementary strip slot with different degrees of asymmetry. This illustrative example confirms the usefulness of the proposed topologies, which can be regarded as an extension of the symmetric lattice network, since they preserve the eigenstate decomposition.

Plasmon-Exciton Coupling in Symmetry-Broken Nanocavities

We investigate the onset of strong coupling in the temporal dynamics of the exciton population at a single emitter interacting with symmetry-broken plasmonic nanocavities. These structures consist in pairs of metallodielectric elements separated by a nanometric gap, with different degrees of asymmetry imposed on their geometric or material characteristics. In order to describe the emergence of plasmon-exciton-polaritons in these systems, we extend and generalize a transformation optics method previously applied to dimers of identical particles. This approach provides a natural decomposition of the spectral density in terms of a well-defined set of plasmonic resonances, as well as an insightful description of the coupling strength dependence on the emitter position. On the one hand, we shed light into the low sensitivity of plasmon-exciton interactions to geometric asymmetry in cavities such as nanoparticle-on-a-mirror configurations. On the other hand, our findings reveal that a more complex spatial and s...

Macroscopic Thermal Rectification Device Using Vanadium Dioxide Thin Film

A thermal rectifier is a device in which heat flows in the forward direction but very little can flow in the opposite direction. Because the heat current can be controlled, the device is promising for future practical applications. In this study, the experiments were performed to investigate temperature-gated thermal rectification using macroscopic vanadium dioxide $$(\hbox {VO}_{2})$$ thin films deposited on an asymmetric substrate. The $$\hbox {VO}_{2}$$ phase transition, occurred near 340 K, changed both the electrical and thermal properties. Therefore, we used these properties to investigate the thermal rectification. The $$\hbox {VO}_{2}$$ thin films were prepared on cover glass substrates by RF sputtering with a $$\hbox {VO}_{2}$$ disk target at $$500~{^{\circ }}\hbox {C}$$ . The morphology of the thin films was investigated. Silver paste and a copper band were used to connect the films with a heater and temperature controller. We observed thermal rectification in the temperature range of T = 310 K–370 K in several film samples obtained with different degrees of asymmetry, deposition times, and post-annealing times. It is found that $$60{^{\circ }}$$ triangular-shaped samples have a rectification coefficient of 1.14, and the rectification coefficient is increased with the increasing of the angle. In addition, the two rectangular-shaped samples have the coefficient of 1.06, which could also be enhanced by increasing the ratio of width.

Procedure to identify outliers through cumulative distribution of extremes in a Gamma response model

ABSTRACTThis work aimed at proposing a procedure based on the cumulative distribution of maximums and minimums to identify outliers in generalized Gamma-response models. In order to validate such method, we used simulations scenarios defined by the combination of different samples, contamination rate and distributions with different degrees of asymmetry. In this context, probabilities related to errors in classification and accuracy were obtained by carrying by Monte Carlo simulations. Using cumulative distribution of extremes to identify outliers in a Gamma-response model is recommended, since it is not likely to present errors and was highly accurate in all assessed scenarios.

A Metric for the Quantification of Macrosegregation During Alloy Solidification

A metric for quantifying the degree of solidification macrosegregation is proposed that statistically fits compositional data from experiments and simulations to a three-parameter Weibull distribution. The method for fitting such a distribution is described and examples are presented. The new metrics are compared to existing macrosegregation measures and the Weibull distribution is shown to be the best fit to data. The fitted three-parameter Weibull distribution is generally found to have better agreement with the composition data than a Gaussian distribution, upon which the macrosegregation number is based, because the Weibull better accounts for asymmetry in the dataset. Trends in macrosegregation results are identified using the new metrics, specifically the normalized Weibull deviation, and compared to the trends identified by the macrosegregation number. A grid dependence study is performed using both metrics as tests for convergence. The utility of the Weibull distribution is demonstrated by comparing composition data with different degrees of asymmetry due to different solidification cooling rates. The difference between the values of the two metrics is a measure of the asymmetry in the compositional distribution.