Defect Reduction Research Articles

Review on Hybrid Welding Techniques for Improved Joint Performance

The process of welding is extensively employed in diverse industrial sectors for the purpose of material joining. The integrity of components or structures is significantly dependent on the quality and performance of welded joints. Nevertheless, conventional welding techniques present certain restrictions, including reduced welding velocity, substandard joint characteristics, and deformation. Hybrid welding techniques have surfaced as a viable solution in recent times to address the limitations and enhance the joint performance.The present study provides a thorough examination of diverse hybrid welding methodologies, encompassing laser-arc hybrid welding, friction stir welding, and hybrid laser welding. The manuscript examines the operational mechanisms, benefits, and constraints of every method. Moreover, the paper presents findings from recent research studies that have examined the collective efficacy of these methodologies across various materials and contexts.The findings indicate that the utilisation of hybrid welding methods has the potential to enhance joint performance through the improvement of mechanical properties, reduction of defects, and minimization of distortion. The manuscript additionally examines the obstacles and prospective avenues in the realm of hybrid welding. The research presented herein offers significant insights for both researchers and practitioners operating within the welding industry. Specifically, it provides guidance on the selection of optimal welding techniques for applications, as well as the optimisation of welding parameters to enhance joint performance.

Effect of local and systemic administration of atorvastatin for improving bone healing on critical defects.

This study aimed to evaluate the impact of atorvastatin, administered both locally and systemically, on critical defects in the calvaria of rats. Thirty-six adult rats were randomly assigned to three groups, with all bone defects covered by a collagen membrane. The groups received different treatments: distilled water (GAD), where membranes were soaked in distilled water; systemic application of atorvastatin (GAS) at a dosage of 3.6mg/kg/day through gavage; and local application of atorvastatin (GAL). After 14 and 28 days, all animals were euthanized, and various assessments were conducted, including histometric analysis, measurement of linear residual defect, evaluation of newly formed bone area, determination of membrane and soft tissue area, cell count, and immunohistochemical analysis. Group GAS exhibited a significant reduction in residual defect compared to the other groups (p<0.05) and a lower number of osteocytes (p<0.05) in comparison with other groups. On day 28, both GAL and GAS groups showed a higher number of inflammatory cells compared to GAD (p<0.05). Immunolabeling of CD31 was similar for both groups, but in the case of osteocalcin, there was a significant increase in labeling for groups GAS and GAL between days 14 and 28 postoperative (p<0.05). In conclusion, systemic atorvastatin demonstrated enhanced osteogenesis in critical calvaria defects in rats, suggesting its efficacy in promoting bone regeneration without exerting a notable anti-inflammatory effect.

Dimensional reduction and emergence of defects in the Oseen-Frank model for nematic liquid crystals

Dimensional reduction and emergence of defects in the Oseen-Frank model for nematic liquid crystals

Analysis of dislocation defects in compositionally step-graded α-(Al x Ga1-x )2O3 layers.

The ultra-wide bandgap semiconductor α-Ga2O3 can be heteroepitaxially grown on a sapphire substrate. However, due to a lattice mismatch of about 4.6% with a sapphire substrate, many dislocation defects occur in α-Ga2O3 films. To reduce the dislocation density, compositionally step-graded α-(Al x Ga1-x )2O3 layers were fabricated on a c-plane sapphire substrate using mist CVD. TEM measurements revealed few dislocations in the initial layer of α-(Al0.96Ga0.04)2O3, but numerous dislocations were observed in the subsequent layer of α-(Al0.84Ga0.16)2O3. However, the step-graded α-(Al x Ga1-x )2O3 layers exhibited bending of the dislocations under both compressive and tensile strains due to compositional differences of α-(Al x Ga1-x )2O3, resulting in about 50% reduction of the dislocation density in the high-Ga-composition layer of α-(Al x Ga1-x )2O3. The introduction of multiple 50 nm α-Ga2O3 layers into the compositionally step-graded α-(Al x Ga1-x )2O3 layers resulted in a notable reduction in dislocation defects at the interface between the sandwiched α-Ga2O3 layers. It is assumed that the dislocations were bent by the strain caused by the composition change, resulting in a decrease in the number of dislocations. It is anticipated that further reduction of dislocation density will be achieved by optimizing the composition change and thicknesses of layers that provide effective strain for dislocation bending, and by stacking these layers.

A Ni0(cod)(dq) (COD: 1,5-cycloctadiene; DQ: duroquinone) complex as a catalyst precursor for oligothiophene and polythiophene synthesis.

Nickel-catalyzed syntheses of oligothiophene and polythiophene were carried out with Ni(cod)(dq) (COD: 1,5-cycloctadiene; DQ: duroquinone) as a catalyst precursor. Studies on the ligand exchange of Ni(cod)(dq) revealed that a high temperature was necessary to replace COD and DQ with PPh3 and N-heterocyclic carbene IPr. A coupling reaction of a metalated 3-hexylthiophene with 2-chloro-3-hexylthiophene employing Ni(cod)(dq) with IPr proceeded with a remarkably reduced amount of homocoupling byproduct. Polymerization of 2-chloro-3-hexylthiophene with Ni(cod)(dq)/DPPP also resulted in the reduction of the regioregularity defect.

Reduction of injection molded silica glass defects and enhancement of glass quality via water debinding

Pure silica glass has been fabricated by the injection molding and sintering technique. The quality of the as-fabricated silica glass was improved via the water debinding process.

The Role of Rho Kinase Inhibitors in Corneal Diseases.

The cornea, as the outermost layer of the eye, plays a crucial role in vision by focusing light onto the retina. Various diseases and injuries can compromise its clarity, leading to impaired vision. This review aims to provide a thorough overview of the pharmacological properties, therapeutic potential and associated risks of Rho-associated protein kinase (ROCK) inhibitors in the management of corneal diseases. The article focuses on four key ROCK inhibitors: Y-27632, fasudil, ripasudil, and netarsudil, providing a comparative examination. Studies supporting the use of ROCK inhibitors highlight their efficacy across diverse corneal conditions. In Fuchs' endothelial corneal dystrophy, studies on the application of Y-27632, ripasudil, and netarsudil demonstrated noteworthy enhancements in corneal clarity, endothelial cell density, and visual acuity. In pseudophakic bullous keratopathy, the injection of Y-27632 together with cultured corneal endothelial cells into the anterior chamber lead to enhanced corneal endothelial cell density and improved visual acuity. Animal models simulating chemical injury to the cornea showed a reduction of neovascularization and epithelial defects after application of fasudil and in a case of iridocorneal endothelial syndrome netarsudil improved corneal edema. Addressing safety considerations, netarsudil and ripasudil, both clinically approved, exhibit adverse events such as conjunctival hyperemia, conjunctival hemorrhage, cornea verticillata, conjunctivitis, and blepharitis. Monitoring patients during treatment becomes crucial to balancing the potential therapeutic benefits with these associated risks. In conclusion, ROCK inhibitors, particularly netarsudil and ripasudil, offer promise in managing corneal diseases. The comparative analysis of their pharmacological properties and studies supporting their efficacy underscore their potential therapeutic significance. However, ongoing research is paramount to comprehensively understand their safety profiles and long-term outcomes in diverse corneal conditions, guiding their optimal application in clinical practice.

One-step dual-additive passivated wide-bandgap perovskites to realize 44.72%-efficient indoor photovoltaics

A one-step dual-additive strategy enables high-quality wide-bandgap perovskite films with efficient defect passivation, resulting in a certified record PCE of 44.72%, with a high Voc of 1.069 V, and an FF of 82.3% under U30 light.

Biomarkers in retinal detachment surgery. How can we improve visual outcomes

Rhegmatogenous retinal detachment (RRD) is associated with separation of the neurosensory retina from the RPE, leading to visual field defect and potential reduction of central vision. Despite significant improvement in primary and final reattachment rate exceeding 90% and 98% respectively, functional outcomes are still difficult to predict and vary widely. In cases with macular involvement several factors have been implicated in the final visual recovery. These biomarkers are either related to individual risk factors (e.g., duration of symptoms, age, high myopia, and concomitant retinal disease),or to peri and postoperative factors (time to surgery, type of surgery, day of the week, experience of surgeon, positioning before and after surgery, and follow‐up management). With the availability of high‐resolution imaging modalities additional biomarkers have emerged, facilitating further more accurate prediction of visual outcome. Incorporating retinal detachment biomarkers into the daily clinical practice is essential to provide more effective patient counselling and potentially modify the visual rehabilitation process.

Pathological profile of S.P. Botkin infectious hospital during the siege of Leningrad (1941-1944)

The results of autopsies performed in the pathological department of the Infectious Diseases Hospital named after. S.P. Botkin during the siege of Leningrad (from September 8, 1941 to January 27, 1944). The structure of diseases of the deceased varied during different periods of the siege of Leningrad. In the first period (September-December 1941), diphtheria, dysentery, measles, typhoid fever, and scarlet fever prevailed among the diseases. The most common causes of death in the second period (April-December 1942) were typhus, dysentery, tuberculosis, lobar pneumonia, and typhoid fever. Nosological structure in the third period of the blockade (January 1943 - January 1944): tuberculosis, dysentery, cachexia, lobar pneumonia, infectious jaundice. The discrepancy between clinical and morphological diagnoses is most often noted for the following nosology: pulmonary tuberculosis, typhoid fever, pneumonia, stomach and hepatopancreatobiliary cancer, measles, influenza. The first period of the blockade was distinguished by a high specific proportion of examination of children's bodies - 51.2% of all autopsies; in subsequent periods, the specific share of autopsies of deceased adults (20-59 years) increased to 76.2%. The difference in the nosological structure and age groups of those who died during different periods of the siege of Leningrad was determined by the epidemiological situation in the city, social and living conditions and medical and organizational factors. Conducted in the pathological-anatomical department of the hospital named after. S.P. Botkin during the siege of Leningrad, pathological studies made it possible to timely establish the causes of deaths and identify the peculiarities of the course of infectious diseases against the background of cachexia. Regularly held clinical and anatomical conferences contributed to the reduction of defects in the diagnosis and treatment of infectious diseases.

Integration of Process Modeling and Six Sigma for defect reduction: A case study in a wind blade factory

The energetic and environmental crisis currently being experienced around the world has brought an exponential growth on the demand for wind energy, and, consequently, real challenges for companies in this sector. Since this industry is relatively new, its production processes require a significant amount of human intervention and have a high variability in the process and high lead times. Therefore, there is a need to focus on the quality of the processes and their improvement. This paper presents the use of the Six Sigma DMAIC approach integrated with Business Process Management, to reduce the number of defects and the repair time in a leading wind blade manufacturing company in Portugal. During the measurement and analysis phases, data was collected to understand the performance of the process and to identify the main problems and their causes. The data was analysed through several graphical and statistical techniques. In the analysis phase, process modeling was also utilized, using Business Process Model and Notation, to identify the critical steps that are responsible for producing the majority of defects. One month after beginning to use this approach, it was possible to notice a reduction in the number of defects by more than 30%, in the repair time by 14%, and an increase in the process sigma level by more than 100%. Thus, this hybrid approach has allowed the company to become more competitive and responsive to the constant growth in demand.

Tailoring the buried interface with self-assembled 2-chloroethylphosphonic acid for defect reduction and improved performance of tin-based perovskite solar cells

By using self-assembled molecules to modulate the buried interface between the PEDOT:PSS and the tin-based perovskite film, the efficiency and stability of tin-based perovskite solar cells can be effectively enhanced.

Molecular engineering with CuanCl for effective optimization of a defective interface for wide-bandgap perovskite solar cells

Molecular engineering with CuanCl forms a coordination bond with under-coordinated Pb2+ and an ionic bond with negatively charged defects, resulting in effcient defect reduction for stable wide-bandgap perovskite solar cells.

Enhancing Quality across Industries: A Systematic Literature Review on the Impact of Six Sigma

Purpose: The objective of this study is to conduct a systematic literature review on the impact of Six Sigma in various industries.&#x0D; Design/methodology/approach: A total of 83 articles from respected international journals published between 2015 and 2020 were selected and analyzed. The inclusion criteria ensured that the articles focused on quality improvement using the Six Sigma approach and were published by reputable publishers.&#x0D; Findings: The f indings of the s tudy reveal that manufacturing emerged as the most prevalent sector, with 17 studies dedicated to it. Among the selected articles, case studies were the most employed research method, accounting for 59 studies. Moreover, the study highlights the primary benefits associated with implementing Six Sigma. The most notable benefit is the reduction of defect rates, followed by improvements in efficiency and cost reduction. the primary benefit of Six Sigma is the reduction of defects (52 cases or 42.75%), followed by improvement in efficiency (49 cases or 37.40%), and then cost reduction (26 cases or 19.85%).&#x0D; Research limitations/implications: Based on the results, the study recommends that organizations adopt Six Sigma to enhance the quality of their processes, increase efficiency, and minimize costs.&#x0D; Originality/value: T his recommendation is p articularly relevant f or t he m anufacturing s ector, which s howcased the highest concentration of research studies in the literature.

Іmprovement of performance characteristics and increase of productivity in the production of rolled-welded steel pipes

Thin-sheet cold-rolled 08kp steel is widely used in the production of two-layer copper-plated rolled-soldered tubes by complex processes of cold deformation with metal extraction and subsequent soldering. Problem. For high-quality molding, steel must have high technological plasticity, which is ensured by recrystallization annealing of rolls of rolled steel in periodic garden hood furnaces. It is impossible to obtain a sheet with increased properties, to correct the lack of sheet blanks due to poor-quality deformation, to prevent the subsequent aging of steel over time by processing in hood furnaces. During the manufacture of tubes, annealing of blanks, forming and soldering are carried out in different workshops of the enterprise, which is definitely not economical. Goal. The aim of the work is to improve both the technological and service characteristics of 08kp steel, intended for the manufacture of rolled soldered tubes, and to ensure the possibility of combining all processes of their production in a single line. To achieve the goal, it is necessary to develop an optimal mode of high-speed weakening heat treatment of riveted rolled steel and to study the possibility of replacing soldering in a muffle furnace with high-speed induction soldering. Methodology. The cold-rolled strip was subjected to continuous annealing at 700 °C and subsequent aging at 400 °C for 2 minutes using contact heating (~100 °C/s) in an argon atmosphere. Inductive soldering rolled up copper tubes were made at 1150ºС and duration of heating up to 30 seconds. After soldering, the tube was cooled in a thermostat with argon to a temperature of 900 – 950ºС and subjected to tempering at 600 – 650ºС lasting up to 2 s to prevent deformation aging. Result. Two-stage high-speed heat treatment (recrystallization tempering and aging) guarantees 08kp steel a high level of properties for defect-free forming of small-diameter tubes. High-speed induction soldering allows you to combine all processes in one current line. Practical value. The unification of all tube manufacturing processes in one current line ensures the improvement of their quality, surface cleanliness, absence of aging, reduction of defects and increase of production productivity, reduction of transport costs of manual labor and the number of working personnel. Tubes manufactured using the developed technology passed 100% incoming inspection under production conditions.

Improving the quality of cold-rolled deformable aluminum alloy billets

A mode of high-speed recrystallization annealing has been developed to increase technological plasticity while maintaining the strength of sheet cold-rolled blanks made of deformable aluminum alloys that are not strengthened by heat treatment. Problem. Cold deformation of cold-rolled plates is achieved by recrystallization annealing in hooded furnaces. However, such annealing often does not provide the technological plasticity for defect-free stamping of products and, as a result, has significant rejects. Hooded furnaces are not suitable for improving the deformation of individual billets. In addition, for products with complex configurations that operate in harsh environments, the requirements for rolled aluminum are increased, which is also not possible to realize in open hearth furnaces. These problems can be solved by high-speed continuous parting heat treatment. Goal. The aim is development of a high-speed recrystallization annealing regime for increasing technological plasticity while maintaining the strength of cold-rolled sheet billets from deformable aluminum alloys. Methodology. The object of the study was thin-sheet (1 mm) billets from cold-rolled aluminum alloys AD1, AMts, AMg3. Strip blanks were subjected to high-speed continuous recrystallization annealing using contact heating. The metal was heated at a rate of 5 ºC/c to temperatures from 250 to 400 ºC with an interval of 50 ºC with a holding time of 5 - 15 min at the heating temperature and cooling in air. The quality of the annealing was judged by the nature of the obtained structure and indicators of mechanical properties. The ability to extract metal in different states was evaluated by the Eriksen method. Result. The least energy-consuming modes of continuous high-speed annealing of workpieces from the studied alloys were developed to obtain increased plasticity indicators (while maintaining strength) and improve cold pressure processing in the manufacture of products of complex configuration. Practical value. High-speed recrystallization annealing provides reduction of defects, saving of metal, improvement of productivity in the production of thin-sheet items by the method of cold deformation with deep and complex drawing.

Reduction of surface defects by optimization of casting speed using genetic programming: An industrial case study

Štore Steel Ltd. produces more than 200 different types of steel with a continuous caster installed in 2016. Several defects, mostly related to thermomechanical behaviour in the mould, originate from the continuous casting process. The same casting speed of 1.6 m/min was used for all steel grades. In May 2023, a project was launched to adjust the casting speed according to the casting temperature. This adjustment included the steel grades with the highest number of surface defects and different carbon content: 16MnCrS5, C22, 30MnVS5, and 46MnVS5. For every 10 °C deviation from the prescribed casting temperature, the speed was changed by 0.02 m/min. During the 2-month period, the ratio of rolled bars with detected surface defects (inspected by an automatic control line) decreased for the mentioned steel grades. The decreases were from 11.27 % to 7.93 %, from 12.73 % to 4.11 %, from 16.28 % to 13.40 %, and from 25.52 % to 16.99 % for 16MnCrS5, C22, 30MnVS5, and 46MnVS5, respectively. Based on the collected chemical composition and casting parameters from these two months, models were obtained using linear regression and genetic programming. These models predict the ratio of rolled bars with detected surface defects and the length of detected surface defects. According to the modelling results, the ratio of rolled bars with detected surface defects and the length of detected surface defects could be minimally reduced by 14 % and 189 %, respectively, using casting speed adjustments. A similar result was achieved from July to November 2023 by adjusting the casting speed for the other 27 types of steel. The same was predicted with the already obtained models. Genetic programming outperformed linear regression.

Application of Failure Mode and Effect Analysis (FMEA) for Defect Reduction: A Case Study on Scratch Defects in Oil Separator Parts in Machining Line

This study addresses the problem of significant defect rates on Oil Separator Parts in machining line, especially focusing on scratch defects. The defect rate reached 0.495%, exceeding the company's target of 0.1%. In the approach using FMEA, potential failure modes were identified and rated based on Risk Priority Number to plan corrective actions. Effort and Impact Analysis was used to analyze the most effective action recommendations. Implementation of the 5S methodology was selected as the improvement solution, which focused on workplace organization, maintenance, and cleanliness. The results were positive, with the number of defects decreasing dramatically from 540 to 67 units in July 2023, and the defect rate dropping from 0.495% to 0.145%. Although the company's quality targets have not been fully achieved, the FMEA approach and 5S implementation have been shown to significantly improve production quality and reduce defects. This study proves that this approach has the potential to address complex quality issues, although further challenges may be required to achieve the final goals set.

Multidentate anchoring strategy for synergistically modulating crystallization and stability towards efficient perovskite solar cells

CsFAMA-based perovskite solar cells (PSCs) have become promising photovoltaic materials due to their excellent photovoltaic properties. However, the inherent instability of perovskite severely hinders its commercialization, since the typical ionic nature of perovskite can cause the ionic migration and volatilization of organic components. Herein, allantoin molecules with multiple alternating carbonyl (C = O) and amino (–NH2 or –NH–) groups were introduced as a multidentate additive to synergistically anchor the perovskite components and passivate the defects, resulting in non-radiative recombination and ion migration being not susceptible to occur. Due to the favorable attraction ability of allantoin to the perovskite precursor monomers and the formation of hydrogen bonds between FAI/MAI and allantoin, the crystal quality of perovskite was significantly improved and the bulk/interface defects were effectively eliminated. Specifically, the interaction between allantoin and FA+/MA+ can suppress their deprotonations and prevent the volatilization of organic cations from the initial precursor solutions, drastically reducing the wastage of precursor materials. Consequently, the modified devices demonstrated a prominent elevation of performance with a higher efficiency of 21.49 %, which was better than that of control (19.67 %). Moreover, the modified perovskite films also demonstrated prominent stability under the continuous illumination and moisture aging owing to the reduction of trap defects. The allantoin additives also greatly enhanced the hydrophobicity of perovskite, and the modified device maintained 90 % of its initial efficiency for 1680 h at 10–20 % relative humidity without encapsulation.

Poly(acrylic acid)‐Modified SnO2 Electron Transport Layer for Perovskite Solar Cells

AbstractSnO2 is one of the most used inorganic electron transport materials for organic‐inorganic halide perovskite solar cells. However, the surface defects of SnO2 will block the electron transport at the SnO2/perovskite buried interface and limit the device performance. Here, poly(acrylic acid) (PAA) is employed to modify the SnO2 electron transport layer. Carboxyl groups can react with KOH in the commercial SnO2 aqueous colloidal dispersion to produce potassium polyacrylate, the −COO− can combine not only with oxygen and Sn4+ on SnO2, but also can chelate with uncoordinated Pb2+ defects on perovskite. Moreover, carboxyl groups can form a chemical linker between SnO2 and perovskite via the esterification reaction, leading to the reduction of surface hydroxyl group defects of SnO2. The optimal solar cells with PAA modification achieve an enhanced power conversion efficiency of 18.88 % and improved stability.