FRACTAL COLOR IMAGE COMPRESSION USING A FAST ENCODING ALGORITHM

In this paper a fast fractal encoding algorithm based on the law of cosines is implemented in MATLAB for color images. The implementation results show that the algorithm reduces the average number of searched domain blocks for each range block by a considerable amount as compared to exhaustive search, consequentlyreducing the encoding time. In addition, we get a completely identical fractal code to that of exhaustive search resulting in the same reconstructed image quality. Moreover a general iterative fractal decoding algorithm is also implemented and the PSNRs of the decoded RGB components are plotted against the number of decoderiterations, These convergence plots show that the components reach the fixed point after 6-7 decoding iterations

Design, Modelling, Fabrication, and Testing of Vertical Milling Machine Fixture for Friction Stir Welding Operation

In this work, a simple and robust fixture was designed, modeled, and fabricated for facilitating the friction stir welding process on a vertical milling machine with easy loading/unloading of workpieces. Four different structural materials, i.e., Mild Steel (MS), Grey Cast Iron (GCI), Die Steel (DS), and Hard alloy (HA), were considered for the fixture material. CAD software designed model of the fixture was imported to finite element solver for stress-deformation analysis. From the results of dynamics analysis, Mild Steel showed better performance, i.e., maximum deformation 0.14719 mm and comparable equivalent stress 42.724 MPa as compared to GCI (0.28196 mm, 42.821 MPa), DS (0.15508 mm, 42.821 MPa), and HA (0.17231 mm, 42.821 MPa). Furthermore, MS is commercially available easily than the other three. Therefore, the Mild Steel block was used to fabricate the Friction Stir Welding fixture, and the testing of the fabricated fixture was then carried out by running the FSW experiments. Hardness measurements of the tested specimen proved the practical applicability of fabricated fixture. It was observed that developed fixture reduced set-up time significantly and facilitated a wide range of tool profile machining

Interfacial microstructure, element diffusion, mechanical properties and metallurgical bonding mechanism of 316L-AlSi10Mg multi-material parts fabricated by laser powder bed fusion

This work explored the interfacial microstructure, element diffusion, mechanical properties and metallurgical bonding mechanism of 316L-AlSi10Mg multi-material parts fabricated by laser powder bed fusion (LPBF). Experimental results revealed that insufficient volumetric energy density (VED) of the laser caused lack-fusion porosity in the 316L-AlSi10Mg transition zone, while too high VED produced keyhole-induced porosity defects. Using the optimal process parameters, multi-material parts can be produced with a good interface metallurgical bonding without significant defects. The partial Fe-FCC phase in 316L stainless steel changed into the Fe-BCC structure, and this shift has also changed the preferred orientation of the grains. The intermetallic compound Al5Fe2 and AlFe phases were found in the transition zone. In addition, Al–Fe icosahedral quasicrystals with five-fold symmetry were found at the boundary of the molten pool, which was caused by an extremely high cooling rate. The tensile strength of 316L-AlSi10Mg specimens is higher than that of AlSi10Mg but lower than that of 316L. In contrast to the 316L and AlSi10Mg regions, the fracture mechanism of multi-material fusion zone exhibits a quasi-cleavage fracture mode. The Vickers microhardness of the Al–Fe interface zone was higher than that of 316L with an average value of 235.57 HV0.2 and AlSi10Mg with 124.59 HV0.2, and the interfacial maximum hardness reached 526.68 HV0.2, which was caused by the very hard intermetallic compound Al5Fe2 and AlFe. The metallurgical bonding mechanism of multi-materials was that the dissimilar metals were mixed and in-situ alloyed in the molten pool by the Marangoni convection-induced strong circular flow during LPBF processing

Friction stir alloying of AZ61 and mild steel with Cu-CNT additive

Dissimilar joining between lightweight magnesium (Mg) alloys and steel is essential to produce lighter vehicles, improve vehicles’ fuel efficiency, and reduce carbon emissions. However, the joining of Mg to steel is impractical due to the immiscible properties between these metals. In this experiment, friction stir alloying (FSA) is proposed to solve this problem. The additive, consisting of different wt% of carbon nanotubes (CNT) in Cu powder was first added into the gap between the workpieces and then friction stir welding (FSW) was performed at varied traverse speed and constant rotational speed. After the joining, microstructure characteristics and mechanical properties of Cu-CNT reinforced Mg/steel joints were investigated. Transmission electron microscopy (TEM) analysis of the Mg/steel joint revealed the formation of IMC at the interface of the joint. Further analysis by X-ray diffraction (XRD) showed a dominant presence of Mg2Cu IMC which indicated the interdiffusion of Cu into Mg element to establish intermetallic bonding. The presence of CNT inside the Mg matrix was also confirmed by TEM which contributed to the strengthening effect of the joint. Tensile and microhardness results revealed a notable enhancement of joint mechanical properties when Cu-CNT additive was added as compared to specimens with only Cu additive, and specimens without additive. The enhanced tensile strength and microhardness of the Cu-CNT reinforced Mg/steel joint was attributed to the dispersion of CNT inside the Mg matrix, which induced multiple dislocations in the surface region, therefore improving the mechanical properties of the joint

Research challenges, quality control and monitoring strategy for Wire Arc Additive Manufacturing

Metal additive manufacturing is a high-growth process owing to the capability of producing parts with complicated geometries and custom facets for various applications. The low material input ratio to final part output, in which minimum raw materials are needed to produce complex parts and thin-walled components with a large volume envelop-to-volume ratio, is advantageous compared to the conventional method. The Wire Arc Additive Manufacturing (WAAM) method has undergone significant research and advancement because it can be utilised to produce large metal components at high deposition rates as well as low cost and with better mechanical and microstructural properties than other AM techniques. Because of the significant amounts of processing temperature, various issues and defects arise during the process, hampering high-quality component manufacturing in WAAM. In addition, these components often have an insufficient and poor surface, affecting the metal components' quality. This article reviews common defects and research challenges associated with manufacturing different metal and alloy components using the WAAM process. Various control strategies in WAAM methods, which are essential to reduce or minimise defects to form high-quality metal parts, are summarised. Recent research on implementing artificial intelligence (AI) in quality improvement is discussed. The strategy for quality control using the multi-sensor-based closed-loop system is proposed in conclusion. This strategy could serve as a roadmap for ensuring the deposit efficiency and quality of WAAM components under complex, high-volume manufacturing circumstances

Abstracts of National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020

This book presents the abstracts of the papers presented to the Online National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020 (RDMPMC-2020) held on 26th and 27th August 2020 organized by the Department of Metallurgical and Materials Science in Association with the Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, India. Conference Title: National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020Conference Acronym: RDMPMC-2020Conference Date: 26–27 August 2020Conference Location: Online (Virtual Mode)Conference Organizer: Department of Metallurgical and Materials Engineering, National Institute of Technology JamshedpurCo-organizer: Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, IndiaConference Sponsor: TEQIP-

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London