Local Defects Research Articles

Defect recognition and classification from ultrasonic phased array total focusing method imaging based on domain adaption

Abstract With the rapid development of China’s economy, the demand for oil and gas resources is continuously increasing, leading to the expansion of the scale of oil and gas long-distance pipelines. Consequently, the risk of safety incidents in oil and gas pipelines is on the rise. Welding defects are identified as one of the significant factors contributing to safety incidents in long-distance oil and gas pipelines. In comparison to traditional conventional ultrasonic detection techniques, which exhibit low efficiency and accuracy, ultrasonic phased array detection technology has the capability to accurately detect welding defects in oil and gas long-distance pipelines. This is particularly true with the development of total focusing method imaging technology, enabling quantitative defect analysis and localization in oil and gas long-distance pipelines.However, in the current scenario, analyzing the types of defects in massive data from long-distance pipelines requires human intervention, leading to low detection efficiency and subjective influence on result analysis. Addressing challenges such as low efficiency in human evaluation of defects in ultrasonic phased array detection, low accuracy in traditional image recognition methods, strong subjectivity in manually extracting features, and the absence of a standardized industrial dataset for ultrasonic phased array detection defects, especially in the case of limited data on ultrasonic phased array detection of welding defects, this study focuses on small sample defects in phased array detection images. The study proposes an improved ResNet50 algorithm through domain adaptation in a deep neural network, trained on a large-scale model data, and then applied to ultrasonic phased array detection data. This approach achieves accurate identification and classification of typical volumetric defects (such as pores) and typical area defects (such as cracks) in the phased array detection of welding defects, laying the foundation for intelligent recognition of defects in long-distance oil and gas pipelines.

A Novel Technique for Estimating the Location of Defect or Inception of Water Treeing in the Semiconducting Screen of a Cable

A Novel Technique for Estimating the Location of Defect or Inception of Water Treeing in the Semiconducting Screen of a Cable

A numerical study on the relationship between local defect resonance and sub-harmonic resonance for closed cracks

Abstract The sub-harmonic resonance in closed cracks is caused by resonant properties of the system and the contact of crack surfaces. Local defect resonance is considered a potential resonant phenomenon near cracks. This study compares local resonance and sub-harmonic resonance in a surface-breaking crack using numerical simulations. The authors previously simulated nonlinear sub-harmonic resonance using the harmonic balance-boundary element method. The investigation of local defect resonance utilizes both the boundary element method and the Sakurai-Sugiura method. The numerical results indicate a strong relation between the vibration fields of sub-harmonic frequency components and local defect resonance.

Intraretinal Retinal Pigment Epithelium Cells in Age-Related Macular Degeneration

PurposeTo examine intraretinally migrated retinal pigment epithelium cells (iRPECs) in enucleated human eyes with various retinal conditions and corresponding intraretinal hyperreflective bodies (iHRBs) in a large cohort of patients with age-related macular degeneration in China. DesignPopulation-based study and histomorphometric investigation. Participants/Material: Participants of the population-based Beijing Eye Study, and enucleated human eyes. MethodsOptical coherence tomography (OCT)-based and fundus photography-based examination of the macula of the Beijing Eye Study participants, and light-microscopical histomorphometry of enucleated human eyes. Main Outcome MeasurePresence and location of iRPECs and iHRBs. ResultsIn the Beijing Eye Study (6551 eyes;3301 participants), prevalence of intermediate AMD and late AMD was 331 (5.1%) and 44 (0.6%), respectively. All 42 eyes with intermediate AMD and macular hyperpigmentation had iHRBs at locations corresponding spatially with macular hyperpigmentations on the fundus photographs. Among all eyes with intermediate AMD (n=331), iHRBs were detected in 262 (79.2%) eyes. The most internal location of the iHRBs was at the ellipsoid zone in 46 (13.9%) eyes, at the external limiting membrane (ELM) in 45 (13.6%) eyes, and in the outer nuclear layer in 145 (43.8%) eyes. Out of the 262 eyes with iHRBs, 186 (71.0%) eyes showed a corresponding defect in the ellipsoid zone, and 128 (48.9%) eyes a defect in the ELM. The eyes with an iHRB located beneath the ELM did not show an ELM defect. The iHRBs were associated with a plume-like appearance and with a smoke-like appearance in 20 (7.6%) eyes and 137 (52.3%) eyes, respectively. All iHRBs did not have a shadow on the OCT images. Similar findings were obtained in the eyes with late AMD. Among 237 eyes examined histologically, 21 globes showed iRPECs: 8 eyes in parapapillary alpha zone/beta zone; 5 eyes with myopic patchy atrophies, 3 eyes with AMD. The iRPECs were spatially associated with an ELM defect and were not surrounded by a basal membrane. ConclusionsIHRBs can be found in 3 out of 4 eyes with intermediate AMD, correlate histologically with intraretinally located (migrated) RPE cells, and correspond spatially with localized defects of the ellipsoid zone and ELM.

Facial Artery Perforator Flap for Perioral and Perinasal Oncologic Defect Reconstruction: Surgical Technique and Postoperative Outcomes.

Facial artery perforator (FAP) flap is a versatile and reliable one-step facial reconstruction technique. However, its full potential remains underutilized due to a lack of clear guidelines and rigorous technique requirements. This study report the use of FAP flaps in our centre for the management of perioral and nasal oncologic defects, focusing on surgical technique performed and post-operative management. We conducted a retrospective review of all patients who underwent reconstruction with a perioral or perinasal FAP flap only following tumor resection over a 4-year period (n = 29). Parameters measured included flap survival, complication rates, surgical technique performed, and the need for touch-up procedures. Patients were grouped based on age, defect size, and location and outcomes were compared across these groups. The mean histological tumor defect area was 331 mm2. During at least 6 months of follow-up, no local recurrence was observed. Twenty-seven (93.1%) flaps survived completely. Major postsurgical complications occurred in seven (23.8%) patients, including complete flap necrosis (1), partial flap necrosis (1), flap collapse (1), venous congestion (1), wound dehiscence (1), and local infection (2). A higher complication rate was associated with nose tip defects (80.0% vs. 12.5%, p = 0.007). Touch-up procedures were more frequently required for reconstructions involving the nasal sidewall and dorsum (53.8% vs. 13.3%, p = 0.04). Based on our experience, the FAP flap is highly effective for the reconstruction of the upper lip, nasolabial fold, and certain oncologic nasal defects. However, specific defect locations, such as the nose tip, may be associated with higher complication rates, necessitating careful patient selection and surgical planning.

Guided Wave–Based Defect Localization via Parameterized FRF-Based Reduced-Order Models

Guided Wave–Based Defect Localization via Parameterized FRF-Based Reduced-Order Models

Detecting Manufacturing Defects on Printed Circuit Boards Using Metamaterial-Based Circular Microstrip Patch Antenna

In this study, a microstrip circular patch antenna is designed having a metamaterial-based (MTM) ground plane to detect manufacturing defects of short circuits and open circuits on printed circuit boards (PCB). In that regard, PCB specimens of FR-4 as the substrate and copper microstrip lines as the conductive wiring lines are designed and manufactured. Five vertical copper lines printed side by side on the top of the substrate are used to demonstrate the working mechanism of the designed antenna sensor. Two different defect scenarios of open and short circuits with controlled locations are studied to determine variations in the return loss data of the proposed structure. MTM cell structures with cross lines enclosed by an octagon ring are periodically placed as part of the ground plane of the proposed antenna to obtain higher sensitivity of the designed and manufactured sensor. Antenna return loss behaviors in terms of the locations of the faults are employed to prepare a database to detect not only the presence of the faults but also determine their locations. Since the samples to be measured are not irreversibly damaged during the testing process, the proposed design can be considered a non-destructive measurement method to provide information about the type and location of defects with real-time measurement data.

Influence of lubrication state transition on dynamic characteristics of deep groove ball bearing with localized defect in thermal environment

The accuracy of the vibration response in a defective bearing dynamics model depends on the precise representation of the lubrication friction state between the rolling element (RE) and the raceway within the model. In this study, a fault dynamic model for outer ring defect of deep groove ball bearings (DGBBs), considering the lubrication state transition in a thermal environment, is established. This model accounts for the asperity contact effect during the lubrication state transition and integrates the lubrication-friction model for temperature changes into the dynamic model when skidding occurs. The influence of lubrication state change on the fault frequency of outer ring of DGBB in thermal environment is studied. The experimental and simulation results indicate that the lubrication state of the bearing is gradually deteriorated from elastohydrodynamic lubrication to mixed lubrication with the increase of working temperature. The transformation of the lubrication state is shown to have a significant effect on friction, resulting in the fault frequency of the outer ring increasing with temperature, which exhibits substantial deviation in the thermal environment. In the temperature range of 30 °C–150 °C, the deviation of defect frequency reaches 15.5%, which affects the accuracy of bearing fault diagnosis. This study may offer recommendations for enhancing the condition monitoring of rolling bearings under extreme working conditions.

Elliptical excision and primary closure of nasal defect to achieve best esthetic outcome: A case series of 50 patients

Objectives: To evaluate the cosmetic result of nasal of an elliptical excision and primary closure on small nasal defect by using Scar assessment using the Stony Brook Scar Evaluation Scale (SBSES) score. Material and Methods: This retrospective interventional study was conducted in a private clinic over a 2-year duration. Patients aged 18–60 years with nasal defects <1.5 cm were enrolled after obtaining informed consent. Exclusion criteria included immunocompromised status, keloidal tendency, local site infection, bleeding disorder, age <18 years, and lack of consent. Scar assessment using the SBSES was performed at the end of 6 months. Statistical analysis included summary statistics, analysis of variance tests, and a significance level of P < 0.05. Results: The study included 50 patients, with 54% males and 46% females. The most common age group was 21–40 years, and melanocytic nevi was the most common cause for excision. Lesions were excised mainly from the lateral wall and dorsum of the nose. The mean SBSES score was 3.79 ± 0.467. The best cosmetic outcome was observed in lesions involving the dorsum followed by the root of the nose. No significant difference was found among the SBSES scores for various subunits. Conclusion: Elliptical excision with primary closure is a simple and effective technique for small nasal defects, providing good cosmetic results. The location of the nasal defect influences the cosmetic outcome, with better results observed in areas with thinner skin and increased skin laxity.

Study on the Effect of Starved Lubrication on the Dynamic Characteristics of Locally Failed Roller Bearings

When the lubricant is not enough to maintain the ideal lubrication state of the bearing, the deep groove ball bearing will enter the starved lubrication state, which leads to the change of the vibration response of the deep groove ball bearing with localized defects. Previous bearing dynamics models mainly consider the lubrication state as an ideal lubrication condition, which may not reveal the effect of starved lubrication on the vibration characteristics of defective bearings. In this paper, the internal interaction of the system under starved condition is taken into account, and a dynamic model of defective deep groove ball bearings with insufficient lubricant is established to investigate the effects of different starved lubrication degrees on the contact force, friction force, cage speed, and system vibration characteristics. The results show that the lubricant insufficiency significantly changes the contact force inside the bearing, and the increase in friction caused by the increase in the degree of starved lubrication leads to the suppression of the degree of bearing slipping. The root mean square (RMS) value of the time-domain signal and the outer ring fault frequency both increase with the increase of the starved degree. The results of the study are helpful for fault diagnosis and condition monitoring of related equipment.

Longitudinal Wave Defect Detection Technology Based on Ablation Mechanism

For laser ultrasound in the thermoelastic mechanism, excitation of ultrasonic body wave signal is weak, it is not easy to realize the detection of deep defects inside the workpiece. While the ablation mechanism produces a high and practical ultrasonic signal-to-noise ratio, this paper is based on the generation mechanism of laser ablation excitation of ultrasonic waves, the establishment of laser ultrasound in the ablation mechanism in the aluminum plate excitation and propagation of ultrasonic numerical model, through the solution, obtained the ultrasonic acoustic field map, discussed the ablation mechanism of the laser ultrasonic body wave acoustic field directionality. Additionally, the preliminary verification of the validity of the model is presented. Then, in order to explore the application potential of high signal-to-noise ratio longitudinal waves in defect detection, defects of different depths are preset in the model for simulation calculations, and waveform and acoustic field analyses are performed on the simulation results to study the ultrasonic propagation paths inside the member and the interaction with the defects, and the transverse position and depth of the internal defects are judged by using B-scan imaging. Finally, experimental validation is carried out. The experimental results are highly consistent with the simulation model, and the defect experiments can qualitatively determine the location of internal defects and verify the practicality and accuracy of the model.

HnRNP R promotes O-GlcNAcylation of eIF4G and facilitates axonal protein synthesis

Motoneurons critically depend on precise spatial and temporal control of translation for axon growth and the establishment and maintenance of neuromuscular connections. While defects in local translation have been implicated in the pathogenesis of motoneuron disorders, little is known about the mechanisms regulating axonal protein synthesis. Here, we report that motoneurons derived from Hnrnpr knockout mice show reduced axon growth accompanied by lowered synthesis of cytoskeletal and synaptic components in axons. Mutant mice display denervated neuromuscular junctions and impaired motor behavior. In axons, hnRNP R is a component of translation initiation complexes and, through interaction with O-linked β-N-acetylglucosamine (O-GlcNAc) transferase (Ogt), modulates O-GlcNAcylation of eIF4G. Restoring axonal O-GlcNAc levels rescued local protein synthesis and axon growth defects of hnRNP R knockout motoneurons. Together, these findings demonstrate a function of hnRNP R in controlling the local production of key factors required for axon growth and formation of neuromuscular innervations.

Promoting Surface Conduction through Scalable Structure Engineering of Flexible Topological Insulator Thin Films

AbstractSpintronics, micro/nanofabrication, and the semiconductor industry are undergoing significant transformations, highlighting the need for flexible technologie. This study examines the possibility of integrating topological insulators (TIs), specifically Bi2Te3 thin films (13–191 nm), into flexible spintronic applications through scalable magneto‐sputtering techniques, and investigates how structural organization influences electrical and topological properties through post‐thermal annealing. Films annealed above 250 °C display improved polycrystalline structure, larger crystallites, fewer local defects, and higher a room‐temperature Seebeck coefficient (S) and resistivity (ρ), suggesting decreased bulk electronic contributions. A metastable transport regime is identified in the temperature‐dependent resistivity of films annealed at 300 °C between 20–100 K; in this range, the thinnest film exhibits markedly metallic behavior, signaling the presence of topological surface states (TSS). Magnetoresistance measurements of as‐grown and annealed films, between 3–20 K, demonstrate weak antilocalization. Applying the Hikami‐Larkin‐Nagaoka model, α‐coefficients are found to scale with thickness from 0.5–1, indicating thickness‐controlled coupling of the TSS. Post‐annealing at 300 °C, the phase coherence length, Lϕ, of the thinner films increases, while the temperature dephasing rate shifts from ∼0.7 (as‐grown) to ∼0.5 (post‐annealing), aligning with expected values for 2D TSS. These are encouraging findings for large‐scale manufacturing flexible TI technologies, without sacrificing tunabilit.

Incorporate biosafe additives into self-healing coating on Mg for enhanced interfacial biocompatibility recovery

Local defects in coatings allow aggressive electrolytes penetrate to the coating/substrate interface, accelerating the corrosion of the exposed Mg substrate and compromising its biocompatibility. In this work, self-healing calcium hydrogen phosphate dihydrate (DCPD) coating incorporated with 3,5-dinitrosalicylic acid (3,5-D) or 5-amino salicylic acid (5-A) is designed on Mg. The results reveal that the self-healing and corrosion resistance performance of DCPD improves after adding 3,5-D/5-A. Namely, incorporating 3,5-D/5-A into DCPD accelerates the self-healing process and repair the coating at the initial stage. The released 3,5-D/5-A additives could adsorb on the exposed Mg surface and combine with the Ca2+ ions to precipitate. The interfacial adsorption mechanism of 3,5-D/5-A additives is disclosed by quantum chemical calculation. The simultaneously responsive adsorption and deposition of additives during coating degradation increase the thickness and compactness of the deposition layer at the coating defects, further inhibiting corrosion and stabilizing pH. These findings suggest taking biocompatibility recovery into consideration of preparing self-healing coating for biomedical applications.

Numerical and experimental investigation on debonding detection in honeycomb sandwich using air-coupled local defect resonance and coda wave analysis

Non-contact ultrasonic testing of debonding in honeycomb sandwich structure has been a major challenge in industry. In this study, the air-coupled local defect resonance (LDR) technique with coda wave analysis is proposed for nondestructive testing (NDT) of debonding in honeycomb sandwich structure. Numerical simulations have been conducted to visualize the LDR behavior of debonding in honeycomb sandwich structure by air-coupled excitations, and a decorrelation analysis method is proposed for determining the interval of coda wave from received signals. Results indicate that the start moment of coda wave should be determined as the time corresponding to decorrelation coefficient exceed to 0.2 and the duration is 2.5 ms. Air-coupled LDR scanning experiments were conducted on the honeycomb sandwich specimens with different deboning. Experimental results indicate that the proposed technique is effective for NDT of the debonding in honeycomb sandwich structures. The research provides an efficiency non-contact ultrasonic NDT method for honeycomb sandwich structure.

The influence of stochastic interface defects on the effective thermal conductivity of fiber-reinforced composites

In this paper, a novel microscopic modeling strategy is proposed to investigate the effective thermal conductivity of composites with consideration of stochastic interface defects. To this end, the subdomain boundary element method combined with asymptotic homogenization is proposed to effectively solve the thermal conduction problem. In order to accurately capture the heat flux on the boundary and the internal region in the representative volume element (RVE), a parameterized sub-cell is constructed to discretize the RVE. On this basis, the influence of stochastic interface defects on the thermal conductivity of composites is investigated by utilizing the Monte Carlo method. Specifically, the effect of the location, length, thickness, and area of the interface defects on the thermal conductivity is investigated. A proportional decrease in the transverse thermal conductivity coefficient is found for interface defect areas ranging from 1% to 10%.

Yolo Based Defects Detection Algorithm for EL in PV Modules with Focal and Efficient IoU Loss

Considering the defect detection issues in electroluminescence (EL) of photovoltaic (PV) cell systems, lots of factors result in performance degradation, including defect diversity, data imbalance, scale difference, etc. Focal-EIoU loss, an effective defect detection solution for EL, is proposed based on the improved YOLOv5. Firstly, by analyzing the detection background and scale characteristics of EL defects, a binary classification is carried out in the system. Subsequently, a cascade detection network based on YOLOv5 is designed to further extract features from the binary-classified defects. The defect localization and classification are achieved in this way. To address the problem of imbalanced defect samples, a loss function is designed based on EIoU and Focal-F1 Loss. Experimental results are illustrated to show the effectiveness. Compared with the existing CNN-based deep learning approaches, the proposed focal loss calculation-based method can effectively improve the performance of handling sample imbalance. Moreover, in the detection of 12 types of defects, the Yolov5 algorithms can always obtain higher MAP (mean average precision) even with different parameter levels (Yolov5m: 0.791 vs. 0.857, Yolov5l: 0.798 vs. 0.862, Yolov5x: 0.802 vs. 0.867, Yolov5s: 0.793 vs. 0.865).

Discontinuous Galerkin schemes for hyperbolic systems in non-conservative variables: Quasi-conservative formulation with subcell finite volume corrections

We present a novel quasi-conservative arbitrary high order accurate ADER (Arbitrary-Derivative) discontinuous Galerkin method allowing to efficiently use a non-conservative form of the considered partial differential system, so that the governing equations can be solved directly in the most physically relevant set of variables. This is particularly interesting for multi-material flows with moving interfaces and steep, large magnitude contact discontinuities, as well as in presence of highly non-linear thermodynamics. However, the non-conservative formulation of course introduces a conservation error which would normally lead to a wrong approximation of shock waves. Hence, from the theoretical point of view, we give a formal definition of the conservation defect of non-conservative schemes and we analyze this defect providing a local quasi-conservation condition, which allows us to prove a modified Lax–Wendroff theorem. Within this formalism, we also reformulate classical results concerning smooth solutions, contact discontinuities and moving interfaces. Then, to deal with shock waves in practice, we exploit the framework of the so-called a posteriori subcell finite volume (FV) limiter, so that, in troubled cells appropriately detected, we can incorporate a local conservation correction. Our corrected FV update entirely removes the local conservation defect, allowing, at least formally, to fit in the hypotheses of the proposed modified Lax–Wendroff theorem. Here, the shock-triggered troubled cells are detected by combining physical admissibility criteria, a discrete maximum principle and a shock sensor inspired by Lagrangian hydrodynamics.To prove the capabilities of our novel approach, first, we show that we are able to recover the same results given by conservative schemes on classical benchmarks for the single-fluid Euler equations. We then conclude the presentation by showing the improved reliability of our scheme on the multi-fluid Euler system on examples like the interaction of a shock with a helium bubble for which we are able to avoid the development of any spurious oscillations.

Blockage dynamics in sewer pipes: investigating snagging, accumulation, and dissipation rates of wet wipes

ABSTRACT The increase in sewer blockages, exacerbated by the COVID-19 pandemic due to improper disposal of non-biodegradable items like wet wipes and sanitary products, along with fats, oils, grease, and the presence of defects in sewers, underscores the need for a more profound understanding of wipes’ contribution to these blockages. This study investigated the probability of wipe snagging on sewer imperfections and their subsequent accumulation and dissipation rates under various conditions through laboratory experiments. Findings indicated a significant variability in the likelihood of wipes snagging (ranging from 93% to 0) and accumulating (ranging from 71% to 0), which was influenced by the defect location and the sewer flow rate. Moreover, the study highlighted a direct relationship between the flow rate in the sewer and the rate at which wipes dissipate. Conversely, an inverse relationship was observed between the size of blockages and the dissipation rate of wipes, with larger blockages typically reducing the speed of this process. Importantly, while dissipation rates at low flow rates are nearly constant regardless of the number of wipes and duration, at medium to high flow rates, dissipation initially increases but levels off after 24 h, demonstrating the persistence of wipe-caused blockages in small-diameter sewer pipes.

Algorithm of surgical treatment for diaphyseal defects of the forearm bones due to gunshot injuries

Introduction In the current system of providing medical aid to wounded servicemen, along with the conservative primary surgical treatment and minimally invasive extrafocal fixation, high-tech surgical interventions of considerable complexity with the use of additive and tissue-engineering technologies have been coming to the forefront. It is necessary to determine their place in the current algorithm of limb bone defect management, which was the substantiation of our study.The purpose of the study was to improve the algorithm for selecting a treatment method for patients with associated gunshot defects of the forearm based on the literature and clinical observations.Materials and Methods We analyzed scientific articles in PubMed and Scientific Electronic Library (eLIBRARY.ru) platforms, published from 2004 to 2024, on the basis of which we could refine the algorithm of treatment method selection for patients with associated gunshot defects of the forearm. The developed algorithm was used to treat 178 patients with gunshot fractures of the forearm.Results The review of the literature established the main provisions and principles that are applied in the reconstruction of the forearm with an associated defect. When choosing the method of bone defect management, a great number of authors tend to build a “reconstructive ladder”, moving from less severe (one bone) and extended defects (small defect up to 2 cm) to more complex (both bones) and massive defect (more than 10 cm). Upon having considered the revealed regularities, we improved the algorithm of surgical treatment of the latter, which is based on two classification principles: defect extention and location. Reconstruction of the forearm as a dynamic system after diaphyseal fractures requires consider the state of the radioulnar joint. The function of the latter depends on the length ratio of the radius and ulna bones. Therefore, we substantiated small (up to 2 cm) forearm bone defects that can be managed by simple surgical methods. Another fundamental addition to the algorithm was the allocation of a patients’ group with a defect of one forearm bone and a fracture of the other bone (defect-fracture); this combination allows avoiding complex surgical methods for reconstruction and use segment shortening.Discussion The treatment of associated forearm defects is challenging, the choice of reconstruction technique remains uncertain, and the required consensus is lacking. Several forearm reconstruction techniques are available, yet there is no reliable evidence of their effectiveness in terms of treatment time, complications, reoperations, and functional recovery.Conclusion The algorithm proposed for the treatment of extensive gunshot-associated defects of the forearm allows us to consider the change in the anatomy, make a surgical plan based on the reconstruction vector, and select optimal surgical techniques.