Symmetric Step Research Articles

Voltage-Dependent Electrochemical Carbon Dioxide Reduction Mechanism Unveiled by Kinetic Monte Carlo Simulation.

The voltage-dependent dynamic evolution of the electrocatalytic carbon dioxide reduction reaction (CO2RR) on Cu-based catalysts is still unclear. Herein, a Kinetic Monte Carlo (KMC) model that tracks the evolution of the CO2RR on the Cu (111)/(100) surface is developed. Using the Density Functional Theory calculated energetics of 178 elementary reactions in CO2RR toward C1-C2 multispecies production, the KMC model predicted CO2RR linear sweep voltammetry and potential-dependent product distribution that agree well with experimental observations. Degree of rate control analysis reveals that, on Cu (111), the primary hydrocarbon product is C1 species CH4, and as the working potential increases, its rate-determining step (RDS) changes from CO hydrogenation toward the CHO* formation step into the COH* formation step. The Cu (100) surface is more active toward C2H4 and CH3CH2OH production with CO* symmetric coupling step as RDS. This KMC model provides important insights into the CO2RR dynamics on Cu catalysts.

Modeling, Analysis, and Comparison of Rectangular Waveguide Structures Having Glide Symmetrical Step Discontinuity with Periodic Dielectric Loading

This paper presents an analysis of the dispersion and |S_21 | frequency characteristics of three periodic structures constructed in rectangular waveguides. Unit cells with dielectric-loaded step discontinuities based on double steps, symmetric double steps, and glide-symmetric double steps were investigated using full-wave electromagnetic simulation software. All dispersion diagram results obtained from the three different models are compared to each other by fixing the period of the unit cell (p = 13.68mm) for each periodic structure. |S_21 | frequency characteristics of the first propagating mode are examined for finite implementations of all considered structures. The transmission characteristics of different numbers of periodic arrangements of each periodic unit cell were investigated. Then, the effect of geometric variations, including glide symmetry, on the transmission characteristics is investigated by keeping the number of unit cells constant (N=10). Furthermore, the filter performance characteristics of the proposed structure are compared with those of the reported studies in the open literature.

Completing the Asymptotic Classification of Mostly Symmetric Short Step Walks in an Orthant

Completing the Asymptotic Classification of Mostly Symmetric Short Step Walks in an Orthant

α,β‐C—C—C Agostic Bonding Interactions in Ruthenacyclobutane and π‐Complex Assisted Olefin Metathesis Catalyzed by Ruthenium‐Alkylidene Complexes

ABSTRACTComputational aspects of concerted [2+2] oxidative‐retrocycloaddition‐cycloreversion reaction through ruthenium alkylidene π‐complexes and ruthenacyclobutane with α,β‐(C—C—C) agostic bonding interactions in olefin metathesis are presented. d6‐Ruthenium carbene complexes, with ruthenium in the oxidation state +2, undergo successive [2+2] cycloaddition and cycloreversion steps, through associative, dissociative, or interchange mechanisms. This process involves coordination of the olefin to 16‐electron Ru complex followed by phosphine dissociation, or first phosphine dissociation then coordination of the olefin to the 14‐electron Ru complex with rearrangement to a ruthenacyclobutane intermediate, followed by symmetrical reverse steps. Donation of σ‐electron density from the two C—C σ‐bonds to the metal center leads to α,β‐(C—C—C) agostic bonds, which stabilized metallacyclobutane as a formally 16‐electron complex, with lower energy than the corresponding π‐complex. In the transformation from π‐complex to ruthenacyclobutane the ruthenium atom is formally oxidized to Ru(IV). The most efficient ligands are those that stabilize the high‐oxidation state metallacyclobutane (IV) intermediate relative to the ruthenium carbene.

Effects of ankle-foot orthosis with dorsiflexion resistance on the quasi-joint stiffness of the ankle joint and spatial asymmetry during gait in patients with hemiparesis

Effects of ankle-foot orthosis with dorsiflexion resistance on the quasi-joint stiffness of the ankle joint and spatial asymmetry during gait in patients with hemiparesis

1 Sex Differences in Middle Cerebral Artery Velocity in Patients with Persistent Post-Concussion Convergence Insufficiency (PPCS-CI)

OBJECTIVES/GOALS: The objective of this study is to investigate the neurophysiological mechanism of vision therapy in male and female adolescents with persistent post-concussion convergence insufficiency (PPCS-CI). This study may improve diagnostics and inform more effective personalized point of care treatment strategies to remediate symptoms. METHODS/STUDY POPULATION: Participants (ages 11-25) were diagnosed with PPCS by a physician, CI was diagnosed by an optometrist and OBVAT was performed by certified therapists. Patients with PPCS-CI were randomly assigned to a therapy type (immediate therapy or natural recovery). Hemodynamic measures were examined in patients with PPCS-CI at baseline (1-3 months post-concussion), and post OBVAT to evaluate recovery outcomes. Non-invasive techniques were used to measure middle cerebral artery velocity (MCAv), blood pressure, heart rate, and end-tidal CO2 at rest and during objective symmetrical convergence step eye movements. Functional magnetic resonance imaging (fMRI) was acquired during convergence step eye movement experiments contrasted to sustained fixation and resting state data collection. RESULTS/ANTICIPATED RESULTS: To investigate the neural mechanism of OBVAT, eye movements, fMRI and physiological measures were collected in 8 patients with PPCS-CI (4 men and 4 women). Results show an 10% decrease in the MCA during 4-degree symmetrical convergent eye movement responses in males post-OBVAT and a 19% increase in MCA during convergent eye movement responses in females. Furthermore, there was a group level activation of the frontal eye fields, which improves post-OBVAT. The beta weights in the left frontal eye fields show a trending decrease in male patients post-OBVAT and trending increase in females. Males had a decrease in MCAv post OBVAT (baseline 83.6 ± 7.5 cm/sec & 75.7 ± 12.5 cm/sec post-OBVAT), while females show a significant increase post-OBVAT (baseline 53.77 ± 5.2 cm/sec & post-OBVAT 65.13 cm/sec ± 12.5). DISCUSSION/SIGNIFICANCE: This initial pilot demonstrates there may be different underlying pathophysiological outcomes associated with a concussion dependent on sex. This work may have direct implications on treatment strategies for male and female adolescent patients with PPCS-CI.

Attempted symmetry affects dynamic gait stability in individuals with lower-limb amputation

Attempted symmetry affects dynamic gait stability in individuals with lower-limb amputation

Application of the Ridden Horse Pain Ethogram to 150 Horses with Musculoskeletal Pain before and after Diagnostic Anaesthesia.

The Ridden Horse Pain Ethogram (RHpE) was developed to facilitate the recognition of musculoskeletal pain. The aim of this study was to document changes in RHpE scores before and after diagnostic anaesthesia was performed to alleviate pain ± when the saddle was changed. One hundred and fifty horses underwent ridden exercise as part of an investigation of poor performance. The RHpE was applied before and after the interventions. Fifty-two (34.7%) horses exhibited a bilaterally symmetrical short step length and/or restricted hindlimb impulsion and engagement. Fifty-three (35.3%) horses had episodic lameness; only forty-five (30.0%) horses were continuously lame. The median maximum lameness grade when ridden was 2/8 (interquartile range [IQR]: 0-3; range: 0-4). Fifty-six (37.3%) horses had an ill-fitting saddle, which was considered likely to influence performance. The median RHpE scores after the interventions (2/24 [IQR: 1-3, range: 0-12]) were significantly lower than before the interventions (9/24 [IQR: 8-11, range: 2-15]) (Wilcoxon signed-rank z = 10.6, p < 0.001). There was no correlation between the RHpE score and maximum lameness grade before diagnostic anaesthesia (Spearman's rho = 0.09, p = 0.262). It was concluded that the absence of overt lameness does not preclude primary musculoskeletal pain. Gait quality and performance can be improved by diagnostic anaesthesia, with substantial reductions in RHpE scores.

Symmetrization of 2D Polygonal Shapes Using Mixed-Integer Programming

Symmetry widely exists in nature and man-made shapes, but it is unavoidably distorted during the process of growth, design, digitalization, and reconstruction steps. To enhance symmetry, traditional methods follow the detect-then-symmetrize paradigm, which is sensitive to noise in the detection phase, resulting in ambiguities for the subsequent symmetrization step. In this work, we propose a novel optimization-based framework that jointly detects and optimizes symmetry for 2D shapes represented as polygons. Our method can detect and optimize symmetry using a single objective function. Specifically, we formulate symmetry detection and optimization as a mixed-integer program. Our method first generates a set of candidate symmetric edge pairs, which are then encoded as binary variables in our optimization. The geometry of the shape is expressed as continuous variables, which are then optimized together with the binary variables. The symmetry of the shape is enforced by the designed hard constraints. After the optimization, both the optimal symmetric edge correspondences and the geometry are obtained. Our method simultaneously detects all the symmetric primitive pairs and enhances the symmetry of a model while minimally altering its geometry. We have tested our method on a variety of shapes from designs and vectorizations, and the results have demonstrated its effectiveness.

Semiexplicit symplectic integrators for non-separable Hamiltonian systems

We construct a symplectic integrator for non-separable Hamiltonian systems combining an extended phase space approach of Pihajoki and the symmetric projection method. The resulting method is semiexplicit in the sense that the main time evolution step is explicit whereas the symmetric projection step is implicit. The symmetric projection binds potentially diverging copies of solutions, thereby remedying the main drawback of the extended phase space approach. Moreover, our semiexplicit method is symplectic in the original phase space. This is in contrast to existing extended phase space integrators, which are symplectic only in the extended phase space. We demonstrate that our method exhibits an excellent long-time preservation of invariants, and also that it tends to be as fast as and can be faster than Tao’s explicit modified extended phase space integrator particularly for small enough time steps and with higher-order implementations and for higher-dimensional problems.

Varying Joint Patterns and Compensatory Strategies Can Lead to the Same Functional Gait Outcomes: A Case Study.

This paper analyses joint-space walking mechanisms and redundancies in delivering functional gait outcomes. Multiple biomechanical measures are analysed for two healthy male adults who participated in a multi-factorial study and walked during three sessions. Both participants employed varying intra- and inter-personal compensatory strategies (e.g., vaulting, hip hiking) across walking conditions and exhibited notable gait pattern alterations while keeping task-space (functional) gait parameters invariant. They also preferred various levels of asymmetric step length but kept their symmetric step time consistent and cadence-invariant during free walking. The results demonstrate the importance of an individualised approach and the need for a paradigm shift from functional (task-space) to joint-space gait analysis in attending to (a)typical gaits and delivering human-centred human-robot interaction.

Lamb Wave Wireless Communication Through Healthy and Damaged Channels With Symmetrical and Asymmetrical Steps and Notches.

Data transmission through solid metallic channels is recommended in certain industries where no other options are proposed, such as nuclear, aerospace, and smart vehicles. In addition to the Faraday shielding effect of electromagnetic waves, another issue related to damage presence due to mechanical loads exists. Severe damage in the transmission channel leads to signal loss at the receiver. For this sake, ultrasonic guided waves, such as Lamb waves, maybe a good substitute since they can propagate through long distances in solid metallic structures. The scope of this work is to build a reliable, reproducible, and high data-rate wireless communication experimental platform, using ultrasonic guided waves, through healthy and damaged plates for industrial usage. The target is to compensate at first for the effect of dispersion, reverberation, scattering, and boundary reflections for the healthy plate. The novelty of this work falls within the performance analysis of the demodulation algorithm based on cross-correlation combined with binary phase-shift keying (BPSK), using a finite-element simulation through healthy and damaged plates with different depths of symmetrical and asymmetrical notches (SN and AN) and steps based on the bit error percentage (BEP). Furthermore, another contribution related to the impact of multiple reflections and mode conversions caused by symmetrical and asymmetrical steps and notches is taken into account. After this, numerical results are validated using an ultrasonic guided wave experimental platform. Results based on BEP analysis prove that the algorithm has successfully compensated for the effect of dispersion and boundary reflections for the healthy plate and multiple reflections and mode conversions for the damaged ones. A highly effective data rate of up to 350 kb/s can be reached even in the presence of severe damage in the transmission channel.

Real-time feedback control of split-belt ratio to induce targeted step length asymmetry

IntroductionSplit-belt treadmill training has been used to assist with gait rehabilitation following stroke. This method modifies a patient’s step length asymmetry by adjusting left and right tread speeds individually during training. However, current split-belt training approaches pay little attention to the individuality of patients by applying set tread speed ratios (e.g., 2:1 or 3:1). This generalization results in unpredictable step length adjustments between the legs. To customize the training, this study explores the capabilities of a live feedback system that modulates split-belt tread speeds based on real-time step length asymmetry.Materials and methodsFourteen healthy individuals participated in two 1.5-h gait training sessions scheduled 1 week apart. They were asked to walk on the Computer Assisted Rehabilitation Environment (CAREN) split-belt treadmill system with a boot on one foot to impose asymmetrical gait patterns. Each training session consisted of a 3-min baseline, 10-min baseline with boot, 10-min feedback with boot (6% asymmetry exaggeration in the first session and personalized in the second), 5-min post feedback with boot, and 3-min post feedback without boot. A proportional-integral (PI) controller was used to maintain a specified step-length asymmetry by changing the tread speed ratios during the 10-min feedback period. After the first session, a linear model between baseline asymmetry exaggeration and post-intervention asymmetry improvement was utilized to develop a relationship between target exaggeration and target post-intervention asymmetry. In the second session, this model predicted a necessary target asymmetry exaggeration to replace the original 6%. This prediction was intended to result in a highly symmetric post-intervention step length.Results and discussionEleven out of 14 participants (78.6%) developed a successful relationship between asymmetry exaggeration and decreased asymmetry in the post-intervention period of the first session. Seven out of the 11 participants (63.6%) in this successful correlation group had second session post-intervention asymmetries of < 3.5%.ConclusionsThe use of a PI controller to modulate split-belt tread speeds demonstrated itself to be a viable method for individualizing split-belt treadmill training.

Maximum and records of random walks with stochastic resetting

We revisit the statistics of extremes and records of symmetric random walks with stochastic resetting, extending earlier studies in several directions. We put forward a diffusive scaling regime (symmetric step length distribution with finite variance, weak resetting probability) where the maximum of the walk and the number of its records up to discrete time n become asymptotically proportional to each other for single typical trajectories. Their distributions obey scaling laws ruled by a common two-parameter scaling function, interpolating between a half-Gaussian and a Gumbel law. The exact solution of the problem for the symmetric exponential step length distribution and for the simple Polya lattice walk, as well as a heuristic analysis of other distributions, allow a quantitative study of several facets of the statistics of extremes and records beyond the diffusive scaling regime.

Resilience Evaluation of the Existing Shield Tunnel Lining Induced by the Symmetrical Excavation of Adjacent Foundation Pit Based on Numerical Simulations

It is very important to evaluate the structural behavior of shield tunnel lining reasonably to ensure the safe operation and maintenance of subway trains. In this paper, by virtue of the resilience theory, the resilience evaluation of the existing shield tunnel lining induced by the symmetrical excavation of adjacent foundation pit is conducted using the numerical simulation. Firstly, the structural behavior index of the shield tunnel lining is defined. Moreover, using the evolution of structural behavior index along with the symmetrical excavation steps of adjacent foundation pit, the calculation method of the resilience index of the shield tunnel lining and grade of resilience are proposed. Secondly, numerical simulation is conducted to compare the degree of influence of three different block symmetrical excavation methods of the adjacent foundation pit on the structural deformation of existing shield tunnel lining. Finally, based on the proposed resilience evaluation method, the structural deformation index and the resilience index of the existing shield tunnel lining are calculated under three different block symmetrical excavation methods, which indicates that the control effect of different block symmetrical excavation methods of the adjacent foundation pit varies greatly. Moreover, it is necessary to adopt the fine excavation method of foundation pit by sections to better control the deformation of the existing shield tunnel lining.

New microstrip multiband filter for modern wireless applications using Kappa substrate material

New microstrip multiband filter for modern wireless applications using Kappa substrate material

Image Denoising Using Nonlocal Regularized Deep Image Prior

Deep neural networks have shown great potential in various low-level vision tasks, leading to several state-of-the-art image denoising techniques. Training a deep neural network in a supervised fashion usually requires the collection of a great number of examples and the consumption of a significant amount of time. However, the collection of training samples is very difficult for some application scenarios, such as the full-sampled data of magnetic resonance imaging and the data of satellite remote sensing imaging. In this paper, we overcome the problem of a lack of training data by using an unsupervised deep-learning-based method. Specifically, we propose a deep-learning-based method based on the deep image prior (DIP) method, which only requires a noisy image as training data, without any clean data. It infers the natural images with random inputs and the corrupted observation with the help of performing correction via a convolutional network. We improve the original DIP method as follows: Firstly, the original optimization objective function is modified by adding nonlocal regularizers, consisting of a spatial filter and a frequency domain filter, to promote the gradient sparsity of the solution. Secondly, we solve the optimization problem with the alternating direction method of multipliers (ADMM) framework, resulting in two separate optimization problems, including a symmetric U-Net training step and a plug-and-play proximal denoising step. As such, the proposed method exploits the powerful denoising ability of both deep neural networks and nonlocal regularizations. Experiments validate the effectiveness of leveraging a combination of DIP and nonlocal regularizers, and demonstrate the superior performance of the proposed method both quantitatively and visually compared with the original DIP method.

Load sequence effects and cyclic deformation behaviour of 7075-T651 aluminium alloy

Load sequence effects and cyclic deformation behaviour of 7075-T651 aluminium alloy

Density and polarization of active Brownian particles in curved activity landscapes.

Suspensions of motile active particles with space-dependent activity form characteristic polarization and density patterns. Recent single-particle studies for planar activity landscapes identified several quantities associated with emergent density-polarization patterns that are solely determined by bulk variables. Naive thermodynamic intuition suggests that these results might hold for arbitrary activity landscapes mediating bulk regions, and thus could be used as benchmarks for simulations and theories. However, the considered system operates in a nonequilibrium steady state and we prove by construction that the quantities in question lose their simple form for curved activity landscapes. Specifically, we provide a detailed analytical study of polarization and density profiles induced by radially symmetric activity steps, and of the total polarization for the case of a general radially symmetric activity landscape. While the qualitative picture is similar to the planar case, all the investigated variables depend not only on bulk variables but also comprise geometry-induced contributions. We verified that all our analytical results agree with exact numerical calculations.

Efficient quantum digital signatures without symmetrization step.

Quantum digital signatures (QDS) exploit quantum laws to guarantee non-repudiation, unforgeability and transferability of messages with information-theoretic security. Current QDS protocols face two major restrictions, including the requirement of the symmetrization step with additional secure classical channels and the quadratic scaling of the signature rate with the probability of detection events. Here, we present an efficient QDS protocol to overcome these issues by utilizing the classical post-processing operation called post-matching method. Our protocol does not need the symmetrization step, and the signature rate scales linearly with the probability of detection events. Simulation results show that the signature rate is three orders of magnitude higher than the original protocol in a 100-km-long fiber. This protocol is compatible with existing quantum communication infrastructure, therefore we anticipate that it will play a significant role in providing digital signatures with unconditional security.