Single Localized Defect Research Articles

The Loschmidt spectral form factor

The Spectral Form Factor (SFF) measures the fluctuations in the density of states of a Hamiltonian. We consider a generalization of the SFF called the Loschmidt Spectral Form Factor, textrm{tr}left[{e}^{i{H}_1T}right]textrm{tr}left[{e}^{-i{H}_2T}right] , for H1 − H2 small. If the ensemble average of the SFF is the variance of the density fluctuations for a single Hamiltonian drawn from the ensemble, the averaged Loschmidt SFF is the covariance for two Hamiltonians drawn from a correlated ensemble. This object is a time-domain version of the parametric correlations studied in the quantum chaos and random matrix literatures. We show analytically that the averaged Loschmidt SFF is proportional to eiλTT for a complex rate λ with a positive imaginary part, showing in a quantitative way that the long-time details of the spectrum are exponentially more sensitive to perturbations than the short-time properties. We calculate λ in a number of cases, including random matrix theory, theories with a single localized defect, and hydrodynamic theories.

OEIS Syndrome: Omphalocele, Exstrophy of the Cloaca, Imperforate Anus, and Spinal Defects

OEIS Syndrome: Omphalocele, Exstrophy of the Cloaca, Imperforate Anus, and Spinal Defects

Topographic Relationship with a Retinal Nerve Fiber Layer Defect Differs between β-Zone and γ-Zone Parapapillary Atrophy.

Introduction γ-Zone parapapillary atrophy (PPA), an associated feature in myopic tilted optic disc, is considered to be relevant with glaucomatous optic nerve damage in myopic eyes. This study determines the topographic relationship of γ-zone PPA with a retinal nerve fiber layer defect. Purpose To determine the topographic relationship of γ-zone PPA with a RNFL defect and to compare it with that of β-zone PPA. Design Cross-sectional, observational study. Participants. Eighty-nine eyes from 89 patients with primary open-angle glaucoma who had β-zone PPA (n = 49) or γ-zone PPA (n = 40) and a single localized RNFL defect. Methods PPA was classified according to the presence or absence of Bruch's membrane on the PPA bed in spectral-domain optical coherence tomography. The angular location of the point of maximum radial extent of PPA (PMRE) and the RNFL defect was measured with the fovea-disc axis set at 0° in color and red-free fundus photographs. Main Outcome Measures. Angular distance between the RNFL defect and the PMRE. Results There was no significant intergroup difference in the extent of the RNFL defect (P=0.920). The angular distance between the RNFL defect and the PMRE was significantly greater in γ-zone than β-zone PPA (26.49 ± 17.27° vs. 60.31 ± 17.12°, P < 0.001). The angular location of the PMRE was significantly correlated with the location of the RNFL defect in the β-zone group (r = 0.822, P < 0.001) but not in the γ-zone group. The RNFL defect was mostly located near the edge of γ-zone PPA in the γ-zone group (10.56 ± 9.47°). Conclusions An RNFL defect was observed near the edge of PPA in eyes with γ-zone PPA, in contrast to it being close to the PMRE in eyes with β-zone PPA.

On the relevance of generalized disclinations in defect mechanics

The utility of the notion of generalized disclinations in materials science is discussed within the physical context of modeling interfacial and bulk line defects like defected grain and phase boundaries, dislocations and disclinations. The Burgers vector of a disclination dipole in linear elasticity is derived, clearly demonstrating the equivalence of its stress field to that of an edge dislocation. We also prove that the inverse deformation/displacement jump of a defect line is independent of the cut-surface when its g.disclination strength vanishes. An explicit formula for the inverse deformation jump of a single localized composite defect line in terms of given g.disclination and dislocation strengths is deduced based on the Weingarten theorem for g.disclination theory (Weingarten-gd theorem) at finite deformation. The Burgers vector of a g.disclination dipole at finite deformation is also derived.

Super-harmonic resonance characteristic of a rigid-rotor ball bearing system caused by a single local defect in outer raceway

The studies on dynamics of a fault bearing system are prevalent in recent years, however, we are studying a completely different frequency range than the one where the bearing faults are best seen. Considering a local defect on outer raceway, a two-degree-of-freedom analytical model of a rigid-rotor ball bearing system is established. Three pulse force models are introduced to simulate the local defect. The frequency domain method—harmonic balance method with alternating frequency/time domain technique (HB-AFT) is used to calculate the response in a large frequency range. By comparing the performance at different frequencies, the fault systems with different defect models and parameters reveal the super-harmonic resonances, and the reasons for this phenomenon are uncovered as well. Finally, the theoretical calculation is verified qualitatively by the experimental results, through comparing the frequency spectrums of the defective bearing rotor system to the fault-free one. Therefore, the super-harmonic resonances can be regarded as a dynamic feature. Besides, the obvious super-harmonic resonances indicate the magnification of the harmonics of the “characteristic defect frequency” for outer race in the corresponding speed regions, which may be helpful for the diagnosis of a rotor ball bearing system with a local defect.

Near-field transport imaging applied to photovoltaic materials

We developed and applied a new analytical technique—near-field transport imaging (NF-TI or simply TI)—to photovoltaic materials. Charge-carrier transport is an important factor in solar cell performance, and TI is an innovative approach that integrates a scanning electron microscope with a near-field scanning optical microscope, providing the possibility to study luminescence associated with recombination and transport with high spatial resolution. In this paper, we describe in detail the technical barriers we had to overcome to develop the technique for routine application and the data-fitting procedure used to calculate minority-carrier diffusion length values. The diffusion length measured by TI agrees well with the results calculated by time-resolved photoluminescence on well-controlled gallium arsenide (GaAs) thin-film samples. We report for the first time on measurements on thin-film cadmium telluride using this technique, including the determination of effective carrier diffusion length, as well as the first near-field imaging of the effect of a single localized defect on carrier transport and recombination in a GaAs heterostructure. Furthermore, by changing the scanning setup, we were able to demonstrate near-field cathodoluminescence (CL), and correlated the results with standard CL measurements. The TI technique shows great potential for mapping transport properties in solar cell materials with high spatial resolution.

Tunable Sonic Crystals Assisted Sound Absorber with a Single and Multi Local Defect

In this paper, we emphasize on the experimental study of absorption properties of tunable sonic crystal assisted sound absorber regarding replacement of sonic crystal unit with an artificial single and multi local defect element. Nine pieces of Helmholtz resonators was constructed in a three row to form square 3x3 resonators unit sound absorber model. The influence of a single and multiple Helmholtz resonator manipulation on its sound absorption coefficient was investigated. The experimental results show that the artificial defect manipulation gives the promising possibility for researchers to develop tunable sonic crystals assisted sound absorber. The sound absorber shows a higher sound absorption performance on several different frequency bands associated with the local defect placement position in the sonic crystal structure.

高功率激光系统中缺陷引起的近场调制分析

In high power laser device, near-field beam quality is evaluated through the intensity distribution. However, the measured distribution is a steady state, which can not reflect the evolution features of intensity modulation caused by noise disturbances. Some area encountering serious intensity modulation may be ignored in transmission process. Near-field transmission characteristics of the beam disturbed by noise disturbance are studied. Meanwhile, deeper understanding of the limitations of the measured near-field intensity distribution is obtained. To simplify the analysis of the near-field intensity distribution at different distance under the influence of single local defect, the characteristics of near-field intensity modulation is represented by equivalent Fresnel number. The results show that once a weak modulated information appears in the distribution of measured nearfield intensity, there may be a more serious modulation area before the measurement position. A highest modulation can be up to nine times for a phase type defects with pi delay corresponding to incident intensity.

Topographic correlation between optic nerve head characteristics and retinal nerve fibre layer defect in primary open-angle glaucoma patients: Korea National Health and Nutrition Examination Survey.

To evaluate topographic correlations of the directions of β-zone peripapillary atrophy (PPA) and optic disc torsion with retinal nerve fibre layer (RNFL) defect in a Korean population. Among 292 primary open-angle glaucoma (POAG) patients from the 2012 KNHANES (n = 7444, age ≥ 19 years), 93 eyes of 93 individuals with a single localized RNFL defect were enrolled. The angular locations of the point of maximum radial extent (PMRE) of β-zone PPA and the optic disc torsion were measured on fundus photography. The angular location of the PMRE and the torsion degree (TD) were noted when the absolute value of the former or the latter was ≥15 degrees from the reference line, a line drawn from the centre of the optic disc to the fovea. The overall POAG prevalence was estimated as 4.2% (95% confidence interval [CI], 3.6-4.9). Of the POAG eyes with a single localized RNFL defect, 39.5% had superior or inferior PMRE of β-zone PPA; in 74.9% (p = 0.015) of those cases, the RNFL defect was located in the same hemifield as the angular location of the PMRE. Meanwhile, 40.4% of the POAG eyes with a single localized RNFL defect showed accompanying optic disc torsion. The correlation rate between the direction of the optic disc torsion and the RNFL defect location was 60.2% (p = 0.029). In the Korean POAG patients examined, the directions of the PMRE of β-zone PPA and of the optic disc torsion showed significant associations with the RNFL defect location.

Topographic Correlation between β-Zone Parapapillary Atrophy and Retinal Nerve Fiber Layer Defect

To investigate whether a topographic correlation exists between β-zone parapapillary atrophy (PPA) and retinal nerve fiber layer (RNFL) defect. The location and extent of the β-zone were examined. Retrospective, cross-sectional study. One hundred twenty-eight eyes from 128 consecutive patients with primary open-angle glaucoma (POAG) and a single localized RNFL defect were included. Digital optic disc photographs of the enrolled eyes were reviewed and eyes with β-zone PPA were identified. The topographic parameters of β-zone PPA and RNFL defect were measured on optic disc photographs and digital red-free RNFL photographs. The association between these parameters was examined statistically. Angular location and angular extent of β-zone PPA and RNFL defect, angular location of point of maximum radial extent (PMRE) of β-zone PPA, and β-zone PPA-to-disc area ratio. Eighty-two (64.1%) of the 128 eyes with a single localized RNFL defect had β-zone PPA. Patients with β-zone PPA were younger (by 6.6 years) than those without β-zone PPA (P = 0.001). β-Zone PPA was located most commonly inferotemporally (65.9%). The RNFL defect was located in the same hemifield as the β-zone PPA in 76% of eyes and was located in the same hemifield as PMRE in 88% of eyes. The angular location of the RNFL defect showed a linear correlation with those of β-zone PPA (r = 0.390; P<0.001) and PMRE (r = 0.558; P<0.001). The angular extent of RNFL defect was not correlated significantly with that of β-zone PPA (P = 0.106), but it was associated weakly with β-zone PPA-to-disc area ratio (r = 0.197; P = 0.026). The angular extent of the RNFL defect also was correlated with the cup-to-disc ratio (r = 0.322; P<0.001) and the cup-to-disc area ratio (r = 0.337; P = 0.002). In POAG, a localized RNFL defect is correlated spatially with β-zone PPA.

Interactions between defects and propagating hydrodynamic solitons

This paper studies the hydrodynamic solitons propagating along a long trough with a defective bed. The slight deviation from the plane in the bed serves as the depth defects. Based on the perturbation method, it finds that the free surface wave is governed by a Korteweg-de Vries (KdV) equation with a defect term (KdVD). The numerical calculations show that, for a single-convexity localized defect, the propagating soliton is decelerated as it comes into the defect region, and it is accelerated back to its initial velocity as it leaves, which has a dipole effect. As a result, its displacement is lagged in contrast to the uninfluenced one. And an up-step defect makes the propagating soliton decelerate simply. The opposite influence will occur for a single-concavity localized defect and a down-step one. The defect-induced influence on propagating hydrodynamic solitons depends on the polarity of defects, which agrees with that on non-propagating ones. However, the involved dipole effect of the single localized defect is not displayed in non-propagating cases.

Josephson effect in graphene SNS junction with a single localized defect

Imperfections change essentially the electronic transport properties of graphene. Motivated by a recent experiment reporting on the possible application of graphene as junctions, we study transport properties in graphene-based junctions with single localized defect. We solve the Dirac–Bogoliubov–de-Gennes equation with a single localized defect superconductor–normal(graphene)–superconductor (SNS) junction. We consider the properties of tunneling conductance and Josephson current through an undoped strip of graphene with heavily doped s-wave superconducting electrodes in the limit l def ⪡ L ⪡ ξ . We find that spectrum of Andreev bound states are modified in the presence of single localized defect in the bulk and the minimum tunneling conductance remains the same. The Josephson junction exhibits sign oscillations.

Tunneling conductance of the graphene SNS junction with a single localized defect

We study the electronic transport in a graphene-based superconductor-normal(graphene)-superconductor (SNS) junction by use of the Dirac-Bogoliubov-de Gennes equation. We consider the properties of tunneling conductance through an undoped strip of graphene with heavily doped superconducting electrodes in the dirty limit. We find that spectrum of Andreev bound states are modified in the presence of single localized defect in the bulk. The minimum tunneling conductance remains the same and this result doesn't depend on the actual location of the imperfection.

Understanding the WMAP Cold Spot mystery

The Cold Spot (CS) at galactic coordinates (b = −57°, l = 209°) was discovered in the Wilkinson Microwave Anisotropy Probe (WMAP)data as a cosmic background anomaly. In order to assess the cosmological significance of the Spot, we examine its properties using the cluster analysis of the local extrema in the cosmic microwave background (CMB) signal. We also check the hypothesis that the CMB signal has a non-Gaussian tail, localized in the low-multipole components. We constructed a linear filter, dividing the signal into two parts: non-Gaussian and Gaussian. Using the filter scale as a variable, we can maximize the skewness and kurtosis of the smoothed signal and minimize these statistics. We discovered that the shape of the CS is formed primarily by the components of the CMB signal represented by the multipoles between 10 ≤ ℓ ≤ 20, with a corresponding angular scale of about 5°–10°. This signal leads to the modulation of the CMB on the whole sky, clearly seen at |b| > 30° in both the ILC andWCM maps, rather than in a single localized feature. After subtraction of this modulation, the remaining part of the CMB signal appears to be consistent with statistical homogeneity and Gaussianity. We therefore infer that the mystery of the WMAP Cold Spot reflects directly the peculiarities of low multipoles of the CMB signal, rather than a single local (isolated) defect or the manifestations of a globally anisotropic cosmology.

Defect-induced transitions in synchronous asymmetric exclusion processes

The effects of a single local defect in synchronous asymmetric exclusion processes are investigated via theoretical analysis and Monte Carlo simulations. Our theoretical analysis shows that there are four possible stationary phases, i.e., the (low density, low density), (low density, high density), (high density, low density) and (high density, high density) in the system. In the (high density, low density) phase, the system can reach a maximal current which is determined by the local defect, but independent of boundary conditions. A phenomenological domain wall approach is developed to predict dynamic behavior at phase boundaries. The effects of defective hopping probability p on density profiles and currents are investigated. Our investigation shows that the value of p determines phase transitions when entrance rate α and exit rate β are fixed. Density profiles and currents obtained from theoretical calculations are in agreement with Monte Carlo simulations.