Ring Defects Research Articles

A Defect Detection Method for Grading Rings of Transmission Lines Based on Improved YOLOv8

Detecting defects in aerial images of grading rings collected by drones poses challenges due to the structural similarity between normal and defective samples. The small visual differences make it hard to distinguish defects and extract key features. Additionally, critical defect features often become lost during feature fusion. To address these issues, this paper uses YOLOv8 as the baseline model and proposes an improved YOLOv8-based method for detecting grading ring defects in transmission lines. Our approach first integrates the CloAttention and C2f modules into the feature extraction network, enhancing the model’s ability to capture and identify defect features in grading rings. Additionally, we incorporate CARAFE into the feature fusion network to replace the original upsampling module, effectively reducing the loss of critical defect information during the fusion process. Experimental results demonstrate that our method achieves an average detection accuracy of 67.6% for grading ring defects, marking a 6.8% improvement over the baseline model. This improvement significantly enhances the effectiveness of defect detection in transmission line grading rings.

Bearing fault detection using second-order moment spectrum and adaptive time-varying morphological filtering

The second-order moment spectrum is a method designed to simplify the complex shape of the spectrum, thus facilitating its interpretation for the identification and localization of defects based on peak frequency. Generally used as a final step in defect detection methods, this method offers the advantage of a more easily interpretable spectral shape. Compared to the shape of the spectrum of the vibration signal defined by the Fourier transform, which includes sidebands composed of peaks of large amplitude at different frequencies, the spectrum generated by the second-order moment spectrum method stands out for its simplicity. Starting from the mean and standard deviation of the vibration signal, the second-order moment can be defined as the power of the ratio between the standard deviation and the difference between the signal and the mean. Next, the Fourier transform is applied to express the second-order moment spectrum. The performance of the second-order moment spectrum is evaluated using the principle of comparison with the envelope spectrum obtained by the Hilbert transform. Vibration signals are analyzed using two methods: adaptive time-varying morphological filtering and second-order moment spectrum. After applying these methods to the signals from the database, we observe high-amplitude peaks at the frequencies corresponding to inner ring and ball defects. The second-order moment spectrum gives similar results to those obtained with the Hilbert transform envelope.

Detection method for structural defects of U-shaped hanging ring for power fittings based on magnetic leakage principle

The U-shaped hanging ring of electric power fittings is usually installed outdoors and operates in harsh environments. Under the combined effect of the weight of the conductor and wind load, the bending part at the bottom of the U-shaped hanging ring often experiences wear and cracks due to friction contact, which can easily lead to accidents such as the detachment of transmission lines. Traditional methods for detecting structural defects in ferromagnetic materials, such as ultrasonic testing, eddy current testing, and manual testing, are affected by environmental factors, have a shallow measurement depth, and are difficult to quantify. In order to solve the above problems, this paper proposes a measurement method for detecting structural defects in the U-shaped hanging ring of electric power fittings based on the principle of magnetic leakage. The magnetic leakage signal characteristics of U-shaped hanging ring defects under different excitation structural parameters and different defect types are analyzed. The method of arranging magnetic leakage signal measurement points is studied. The detection of defect parameters is achieved based on the characteristic quantity of the magnetic leakage signal under different defect conditions. Finally, the method is analyzed and verified through examples. The results show that this method can achieve quantitative detection of defect parameters in the U-shaped hanging ring under uniform structural defect and crack structural defect, and has the advantages of high measurement accuracy and small error. The research results of this paper can provide a scientific theoretical basis for the inspection and replacement of transmission line fittings in engineering, which is of great engineering significance for ensuring the safe and stable operation of the power grid.

Investigation on the influence of temperature-variation clearance on the frequency of rolling bearing defects

The clearance between the inner ring (IR) of rolling bearing and rotor is directly proportional to the temperature rise. The increased friction between the IR and rotor, as well as changes in the frequency of rolling bearing defects, and the accuracy of bearing health monitoring decreases. Existing research cannot effectively solve this problem. In response to the above issues, in this paper, the clearance between the bearing IR and the rotor and the internal clearance of bearing were considered, and the clearance was considered as the motion boundary of the rotor inside the IR, dynamic models of the bearing IR, outer ring (OR), and rolling element defects were established, and the trend of rolling bearing defects frequencies with temperature was analyzed, then the rationality of the dynamic models were verified through experimental methods. The research results show that the friction between the rotor and the IR increases with increasing temperature, and the speed of the IR decreases accordingly. The characteristic frequencies of defects in the IR, OR, and rolling element of rolling bearings have decreased by approximately 6.42%, 8.07%, and 6.93% compared to the theoretical values without considering temperature, respectively. This indicates that when identifying the frequency of rolling bearing defects at different temperatures, the frequency deviation caused by the increase in clearance between the IR and the rotor should be considered. The research results may serve as an important basis for fault diagnosis and condition monitoring of rolling bearings.

Paroxysmal impulse vibration analysis of an aero-engine dual-rotor system with a defective inner ring for the inter-shaft bearing

Inter-shaft bearings play a central role in connecting high-pressure (HP) and low-pressure (LP) rotors within aero-engines. Local defects in these bearings can lead to two distinct and complex vibration modes—paroxysmal or continuous impulse vibrations, which arise from the unique installation positions. This study offers a comprehensive exploration of the dynamic phenomena, the underlying physical mechanism, and the analytical conditions for the occurrence of paroxysmal impulse vibrations. The local defects of the inner ring are found to induce paroxysmal impulse vibrations when specific rotational speed ratios between HP and LP rotors are achieved. The dynamic differences and connections between paroxysmal and continuous impulse vibrations are contrasted. Three analytic and explicit prediction formulas are derived, enabling the direct calculation of the operating conditions for paroxysmal impulse vibrations. A summarized prediction flow for paroxysmal impulse vibrations is established. In addition, the proposed prediction formulas and flow allow for the prediction of the precise frequency components of paroxysmal impulse vibrations. In the validation of the simulation results, three experimental cases involving inter-shaft bearings with inner ring defects are conducted, confirming the existence of paroxysmal dynamic phenomena and validating the effectiveness of the proposed prediction formulas and prediction flow for paroxysmal impulse vibrations. Hence, this study offers a novel approach to understanding inter-bearing vibration fault mechanisms.

Simulation method and spectrum modulation characteristic analysis of typical fault signals of inter-shaft bearing

In order to study the frequency spectrum characteristics of the vibration signal of the inter-shaft bearing defect fault in the aero-engine dual-rotor system, a vibration signal mathematical model is established based on the fault characteristic frequency of the inner and outer ring defects of the inter-shaft bearing, and the mutual modulation law of the signals during transmission is analyzed. A test bench for signal transmission path analysis is built to verify the calculation results. The results indicate that the fault signal of the inter-shaft bearing defect significantly attenuates during transmission, and the characteristic frequency of the inter-shaft bearing fault is modulated with the rotor rotation frequency. There are corresponding characteristic frequencies and modulation frequency components in the envelope spectrum of the inter-shaft bearing. The error between the experimental and simulation results is less than 1%, which verifies the accuracy of the simulation calculation results. After being transmitted to the rotor through the inter-shaft bearing, the rotor frequency includes the modulation frequency of bearing varying compliance frequency and rotation frequency, as well as the fault characteristic frequency of the inter-shaft bearing.

Statics and dynamics of point boojums, line and modified Saturn ring topological defects in nematic confined geometry.

In this paper we study the static structure and the dynamics of topological defects associated with isotropic droplets in nematic environment. Investigations were made in confined geometry of optical cells when the droplet size was of the order of or larger than the gap of the cell. We observed the coexistence of point boojums and Saturn ring or modified Saturn ring defects. We found transformation of the Saturn ring defect to two localized broad defects at increasing the droplet size. At droplet coalescence antipodes of point and localized broad defects were born and the dynamics of their annihilation with existing defects was investigated. We found strong difference in the process of annihilation of point and localized broad defects. Microscope images of isotropic droplets in nematic environment in a planar cell. The director orientation far from the droplets is in horizontal direction. The photographs were taken with crossed vertical and horizontal polarizers (a) and with a single horizontal polarizer (b). The cell thickness is 100μm. Droplet diameter is less than the cell thickness. 1 and 2 are point boojums, L is the Saturn ring defect.

A Simulation Investigation on the Influence of Bearing Outer Ring Defect on Dynamic Vibration Characteristics of the Axle‐Box System

AbstractIn this paper, a vehicle track coupling dynamic model including bearing outer ring defects is built, the time history of the axle‐box vibration acceleration and the time history of the bearing roller‐outer raceway contact load under the condition of random track irregularity on the Beijing‐Tianjin line are obtained by simulation calculation. The results show that when the outer ring defect of the bearing occurs, the axle box will generate high‐frequency vibration at the resonance peak in the vertical and lateral directions. When the defect on the bearing outer ring is in the small width of 1 mm, the roller only imposes one impact when passing through the defect area. However, when the width exceeds 3 mm, the large defect causes the roller to impose a double impact on the lateral direction of the axle box, due to changes in bearing clearance in the passing‐through process. When the running speed of the train is about 250 km h−1, the width of bearing outer ring defects needs to be limited to within 1 mm, to minimize a series of problems such as structural fatigue caused by the increased bearing roller‐outer raceway contact load caused by bearing outer ring defects.

Application Improvement of Deep Learning Algorithm in Small-Sized Fittings, Voltage Balancing Ring and Bare Conductor Detection of Transmission Lines

As technological advancements progress and energy conservation and emission reduction policies gain traction, an increasing amount of clean energy is being integrated into the power grid system. This influx of new energy imposes stringent demands on the transmission lines within the power grid system. In recent years, the State Grid has implemented a plethora of intelligent transmission line inspection strategies, with the intelligent inspection of Unmanned Aerial Vehicle (UAV) transmission lines receiving significant promotion and widespread application. However, practical application has revealed that the prevalent transmission line detection algorithms yield a substantial quantity of false detections, particularly in the detection of nut defects in small-sized metallic fittings, voltage balancing ring defects, and defects in uninsulated conductors. To address these issues, this paper employs deep learning algorithms for target detection, critical point detection, and instance segmentation, focusing on aspects such as algorithmic logic, algorithmic models, and data processing. The aim is to enhance the precision of these three types of defect detection, diminish the rate of false detections, and augment the practicality of intelligent grid inspection.

Effect of metal impurities concentration on electrical properties in N-type Recharged-Czochralski silicon

The electrical properties of N-type Recharged-Czochralski (RCz) silicon solar cells are significantly affected by the concentration of metal impurities in the silicon materials. In this work, several N-type RCz silicon ingots were grown using feedstock with different impurities concentration, and the distribution of minority carrier lifetime was tested. It was discovered that a broader range of feedstock impurity concentrations resulted in high and stable minority carrier lifetime of the ingots. Solar cells made from these ingots had an average efficiency of over 24.57%. Meanwhile, the results of impurities segregation calculation and solar cells electroluminescence(EL) test were given. The results indicated that ring defects were the primary cause of differences in electrical properties among silicon ingots produced from feedstock with varying impurity concentrations. Further, the process window to produce high efficiency N-type Czochralski(Cz) silicon solar cells was broadened, and the production cost could be reduced.

Are Non-Six-Membered Ring Defects Formed in Single-Walled Carbon Nanotubes Treated by a Fluorination-Defluorination Process?

Single-walled carbon nanotubes (SWCNTs) modified by introducing non-six-membered ring defects, such as five- and seven-membered rings, have attracted considerable attention because their conductivity is enhanced by increasing the electronic density of states at the Fermi energy level. However, no preparation method exists to efficiently introduce non-six-membered ring defects into SWCNTs. Herein, we attempt to introduce non-six-membered ring defects into SWCNTs by defect rearrangement of the nanotube framework using a fluorination-defluorination process. Defect-introduced SWCNTs were fabricated from SWCNTs fluorinated at 25 °C for different reaction times. Their structures were evaluated, and their conductivities were measured by operating a temperature program. Structural analysis of the defect-induced SWCNTs using X-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and visible-near-infrared spectroscopy did not reveal the presence of non-six-membered ring defects in the SWCNTs but indicated the introduction of vacancy defects. Meanwhile, conductivity measurements performed by operating a temperature program showed that the defluorinated SWCNTs prepared from SWCNTs fluorinated for 3 min (deF-RT-3m) exhibited decreased conductivity owing to the adsorption of water molecules to non-six-membered ring defects, thereby implying the possibility of non-six-membered ring defects being introduced into deF-RT-3m.

Optimal design of thermoelectric properties of graphene nanoribbons with 5-7 ring defects based on Bayesian algorithm

Owing to the huge degree of freedom of structure, the optimal design of thermoelectric conversion performance of defective graphene nanoribbons is one of the difficulties in the field of materials research. In this paper, the thermoelectric properties of graphene nanoribbons with 5-7 ring defects are optimized by using non-equilibrium Green's function combined with Bayesian algorithm.The results show that the Bayesian algorithm is effective and advantageous in the search of graphene nanoribbons with 5-7 ring defects with high thermoelectric conversion efficiency. It is found that the single configuration with the best thermoelectric conversion performance can be quickly and accurately searched from 32896 candidate structures by using Bayesian algorithm. Even in the least efficient round of optimization, only 1495 candidate structures (about 4.54% of all candidate structures) need to be calculated to find the best configuration. It is also found that the thermoelectric value <i>ZT</i> (about 1.13) of the optimal configuration of 5-7 ring defective graphene nanoribbons (21.162 and 1.23 nm in length and width, respectively) at room temperature is nearly one order of magnitude higher than that of the perfect graphene nanoribbons (about 0.14). This is mainly due to the fact that the 5-7 ring defects effectively inhibit the electron thermal conductivity of the system, which makes the maximum balance between the weakening effect of the power factor and the inhibiting effect of the thermal conductivity (positive effect). The results of this study provide a new feasible scheme for designing and fabricating the graphene nanoribbon thermoelectric devices with excellent thermoelectric conversion efficiencies.

High sampling resolution optical coherence tomography reveals potential concurrent reductions in ganglion cell-inner plexiform and inner nuclear layer thickness but not in outer retinal thickness in glaucoma.

To analyse optical coherence tomography (OCT)-derived inner nuclear layer (INL) and outer retinal complex (ORC) measurements relative to ganglion cell-inner plexiform layer (GCIPL) measurements in glaucoma. Glaucoma participants (n= 271) were categorised by 10-2 visual field defect type. Differences in GCIPL, INL and ORC thickness were calculated between glaucoma and matched healthy eyes (n= 548). Hierarchical cluster algorithms were applied to generate topographic patterns of retinal thickness change, with agreement between layers assessed using Cohen's kappa (κ). Differences in GCIPL, INL and ORC thickness within and outside GCIPL regions showing the greatest reductions and Spearman's correlations between layer pairs were compared with 10-2 mean deviation (MD) and pattern standard deviation (PSD) to determine trends with glaucoma severity. Glaucoma participants with inferior and superior defects presented with concordant GCIPL and INL defects demonstrating mostly fair-to-moderate agreement (κ=0.145-0.540), which was not observed in eyes with no or ring defects (κ=-0.067-0.230). Correlations (r) with MD and PSD were moderate and weak in GCIPL and INL thickness differences, respectively (GCIPL vs. MD r= 0.479, GCIPL vs. PSD r= -0.583, INL vs. MD r= 0.259, INL vs. PSD r= -0.187, p= <0.0001-0.002), and weak in GCIPL-INL correlations (MD r= 0.175, p= 0.004 and PSD r= 0.154, p= 0.01). No consistent patterns in ORC thickness or correlations were observed. In glaucoma, concordant reductions in macular INL and GCIPL thickness can be observed, but reductions in ORC thickness appear unlikely. These findings suggest that trans-synaptic retrograde degeneration may occur in glaucoma and could indicate the usefulness of INL thickness in evaluating glaucomatous damage.

Full-circle localization diagnosis of rolling bearing outer ring defects based on double-vibration signal fusion

Localization diagnosis (LD) of rolling bearing outer ring defects plays an important role in failure cause analysis and residual life prediction. This study aims to solve three main issues in the existing LD methods. Firstly, a full-circle functional relationship between outer ring defect and localization index is established based on the dynamics simulation analysis of bearing system. Secondly, the generation mechanism and solution method of the positioning datum are determined using a novel finite element transient dynamic model. Furthermore, variation law of the initial direction of the fault impact under different angular positions is investigated. Lastly, a general localization rule applicable to outer ring defects in the full-circle range is proposed. Therefore, a full-circle localization formula for outer ring defects based on the characteristic fusion of horizontal–vertical signals is proposed. Simulation results verify the effectiveness of the proposed localization formula. Additionally, a morphological filter for LD is investigated to resolve the diagnostic error caused by noise interference in the actual signal. Experimental results show that the presented method can considerably improve diagnostic accuracy.

A correlation of the hydrogen evolution reaction activity to the number of defects formed by the decomposition of doped phosphorus species in carbon nanotubes

Phosphorus-doped carbon materials are one of the novel carbon catalysts for the hydrogen evolution reaction (HER) that have attracted considerable attention in recent years. However, the role of C―P species playing in the HER activity is still not clear. Phosphorus-doped carbon nanotubes were prepared by chemical vapor deposition and annealed at 900, 1000 and 1200 °C to remove all or part of the phosphorus, resulting in four samples with different amounts of substitutional-, pyridine- and pyrrole-like P species. The correlations between the HER activity and the contents of the three species were investigated. Results showed that the content of substitutional P decreased with annealing temperature and none was retained at 1200 °C. The HER activity increased with annealing temperature and the sample annealed at 1200 °C had the highest HER activity in an acid medium with an overpotential of 0.266 V at a current density of 10 mA cm−2. Density functional theory calculations showed that the pentagon- and nine-membered ring defects formed by the elimination of substitutional P mainly contributed to the HER activity.

Passivation of Ring Defects in Czochralski-Grown Silicon Using Magnesium Fluoride Films

This work investigates the potential application of magnesium fluoride (MgFx) films and compares its effectiveness to conventional silicon nitride (SiNx:H) for passivating ring defects, which sometimes occur in n-type Czochralski-grown silicon wafers subjected to high-temperature processes. We find that the passivation of ring defects in MgFx coated samples is fully activated only at 600 °C, whereas passivation in SiNx:H coated samples can be activated by 5 min anneals at 500 °C. Consistent with the passivation activation temperature, energy-dispersive X-ray shows that MgFx films significantly lose fluorine at temperature ≥ 600 °C. Further, subsequent annealing of the previously passivated samples reveals that the ring defects reappear and become recombination-active again. However, this depassivation of the ring defects occurs significantly faster in SiNx:H passivated samples than in MgFx passivated samples at temperatures ≤ 500 °C, whereas the depassivation happens at a rate similar to that at temperatures ≥ 600 °C. Furthermore, in situ monitoring of the change in band–band photoluminescence intensity during annealing also confirms that the passivation and depassivation of ring defects is faster in SiNx:H passivated samples. Based on these observations, we suggest the possibility that the dominant passivating agent in the MgFx and SiNx:H films is fluorine and hydrogen, respectively. Finally, minority carrier lifetime measurements indicate that both the passivation methods improve the bulk lifetime significantly.

Defect-Polymorphism-Controlled Electrophoretic Propulsion of Anisometric Microparticles in a Nematic Liquid Crystal

Nontrivial shape of colloidal particles create complex elastic distortions and topological defects in liquid crystals and play a key role in governing their electrophoretic propulsion through the medium. Here, we report experimental results on defects and electrophoretic transport of anisometric (snowman-shaped) dielectric particles subjected to an alternating electric field perpendicular to the director in a nematic liquid crystal. We demonstrate that the shape asymmetry gives rise to defect-polymorphism by nucleating point or ring defects at multiple locations on the particle and controls the direction as well as the magnitude of the electrophoretic propulsion. Our findings unveil a novel degree of freedom in translocating microparticles in liquid crystals for applications in microfluidics, controlled transport and assembly.

Application of Image Processing Sensor and Pattern Recognition in Detection of Bearing Surface Defects

In order to solve the problem that the traditional detection technology can not meet the requirements of online detection, a visual detection device for bearing inner ring defects based on image processing and pattern recognition is proposed in this paper. The device systematically designs an image acquisition device of bearing inner ring based on CCD. In the hardware scheme, the appropriate lens, camera, light source, and other related hardware are selected according to the actual needs, a complete image acquisition platform of bearing inner ring is built, and the software function design is completed. The simulation results show that the qualified rate of machine detection is 98.6%, the missed detection rate is 0, and the false detection rate is 1.4%, which are better than manual detection. Conclusion. The test results show that the bearing inner ring defect detection system can detect the surface defects of bearing inner ring quickly, stably, and reliably, and the detection efficiency and accuracy are higher than the original manual detection method, so it has a good application prospect.

Charge ambiguity and splitting of monopoles

This paper focuses on topological defects, appearing in mean-field-theory treatments of physical systems such as ultracold atomic gases and gauge field theories. We begin by investigating the ambiguity and addition of topological charges using the mathematical formalism of covering spaces, which clarifies many aspects these phenomena. Subsequently, we classify topological-defect configurations consisting of several monopoles and unknotted ring defects in terms of homotopy groups and fundamental-group actions on them, thus generalizing the previous classifications of a single monopole and a single unknotted ring defect. Finally, we examine the decay of multiply charged topological monopoles under small perturbations of the physical system, and analyze the conditions under which multiply charged monopoles are inclined to split into several singly charged monopoles.

Birth and annihilation of topological defects on the nematic–isotropic interface during droplet coalescence

ABSTRACT In our work, we for the first time observed simultaneous birth and subsequent annihilation of two types of defects on nematic–isotropic interface: point boojums and localised equatorial defects. The investigations were made in the two-phase nematic–isotropic region in nematic droplets with conical boundary conditions. We found a new type of localized defects formed from equatorial ring defects in confined geometry of planar optical cells. During coalescence of nematic droplets, we observed formation of four antipodes of boojums and localised equatorial defects, followed by their pairwise annihilation with existing defects. The dynamics of defect annihilation was investigated.