The present study investigates the effects of laser beam oscillation on the integrity and mechanical behavior of the weld joint by combining both experimental and numerical methodologies for the dissimilar aluminum alloys (AlMg3 AlSiMg). To produce butt joints with different laser power (4-5 kW), speed (67-100 mm/s), oscillation amplitude (0-3 mm), and frequency (0-300 Hz), a high-power single-mode laser was used. A hybrid volumetric heat source was used to develop a fully coupled 3D thermo-mechanical model in COMSOL Multiphysics software to analyze the temperature distribution, weld morphology, residual stresses, and post-solidification distortion. It was found that the sample with power 5 kW and speed 67 mm/s showed the highest tensile strength (249 MPa) but the overall optimum weld performance was achieved when the amplitude of the oscillation was 0.6 mm and the frequency was 200-300 Hz, which minimized residual stresses (from 185 to 172 MPa) and displacements (from 0.036 to 0.017 mm) compared to non-oscillating welds without compromising the tensile strength. Extreme oscillation levels (> 1.8 mm) resulted in poor mechanical behavior. The developed numerical model is an effective and cost-saving tool to minimize the extensive physical experiments to further optimize the weld parameters.

This paper evaluates the successive double-pass laser welding using an adjustable-ring-mode beam for dissimilar AA5754-AA6005 butt welds, benchmarked against single-pass welding. The effects of core-to-ring power ratios and welding configurations on weld geometry, microstructure, porosity formation and mechanical performance are investigated. In single-pass welding, reducing power ratio leads to less weld concavity, grain refinement in the fusion zone, and less porosity. The weld strength increases from 75.7% to 86.6% of AA5754, the weaker base material, when the laser beam shifts from the core-only mode to the core-to-ring power ratio of 0.33. By contrast, double-pass welding, using lower laser power per pass, can produce a shallower fusion zone and a more symmetrical weld profile with reduced weld concavity. Re-melting and re-solidification in the overlap region between two passes is beneficial for reducing weld porosity and disrupting the solidified microstructure, leading to overall grain refinement. The highest joint efficiency is achieved in the double-pass weld with the lowest power ratio of 0.55, reaching 93.5% of AA5754. A more tortuous crack path that deviates in the overlap region and then advances along the second-pass fusion boundary further contribute to the superior strength. These findings highlight the potential of double-pass laser welding as a viable technique for achieving high-quality aluminium welds, particularly for applications where mechanical integrity and dimensional tolerance are critical.

We report a first case of ceftazidime-resistant pediatric melioidosis involving a previously healthy seven-year-old boy who presented with right lobar pneumonia complicated with a 5-cm lung abscess. Ceftazidime was initiated on Day-6 of admission when Burkholderia pseudomallei (ceftazidime-susceptible, minimum inhibitory concentration [MIC] 1.0mcg/mL) was isolated from blood. Despite ceftazidime therapy at the recommended dosage, he developed fulminant septic shock and respiratory failure on Day-18 of hospitalization, requiring invasive ventilation, hemodynamic support, and continuous renal replacement therapy. His antibiotic was empirically escalated to meropenem; ceftazidime-resistant B. pseudomallei (MIC 32mcg/ml) was subsequently isolated from blood and endotracheal secretions. He improved after two weeks of intensive care and was discharged well after two months of hospitalization. Our literature review on ceftazidime-resistant B. pseudomallei infection indicates that acquired resistance is a rare but potentially lethal treatment-related complication. All melioidosis patients should be carefully monitored during treatment with ceftazidime (or other β-lactams) for the development of antimicrobial resistance.

Introduction: A resurgence of pertussis has been reported in numerous countries. This study aimed to determine the incidence, clinical characteristics, and outcome of pertussis among infants in Sarawak, Malaysia. Methodology: We conducted a descriptive retrospective study of infants aged < 12 months with laboratory-confirmed pertussis admitted to Bintulu Hospital in Sarawak, Malaysian Borneo, from 2015 until 2021. Pertussis was confirmed in all patients using a polymerase chain reaction of nasopharyngeal aspirates. Results: Of 588 infants who had a nasopharyngeal aspirate, 108 (18%) had laboratory-confirmed pertussis. The average annual incidence was 482 per 100,000 infants aged < 12 months between 2015 and 2019, with a marked decline in 2020 and 2021. Eighty-two (76%) were < 3 months of age. Seventy-eight (72%) were unvaccinated for pertussis, including 75 (96%) who were too young to receive the first dose. A third of the cases had atypical presentations. Severe disease characterized by hypoxemia, pulmonary hypertension, recurrent apnea, encephalopathy, or cardiovascular dysfunction occurred in 32%. Forty-eight percent required humidified high-flow nasal cannula oxygen therapy and 22% required invasive ventilation. Twenty-four percent overall needed intensive care. One (1%) infant had a fatal outcome. Nearly all cases of severe disease or those that required invasive ventilation or intensive care had received ≤ 1 dose of pertussis vaccination. Conclusions: A high incidence of pertussis with a high rate of severe disease was observed in Sarawak, Malaysia, predominantly among infants too young to be vaccinated. Additional vaccination strategies such as maternal vaccination or cocooning should be considered.

The integration of Intelligent Welding Systems (IWS) in smart manufacturing leverages advancements in sensors, robotics, and artificial intelligence to optimize welding processes. However, in industry practice, we still face challenges such as sufficient data is not available for every manufacturing task, the costs associated with welding data annotation quality, and the risk of knowledge forgetting during the continual welding process. To tackle these issues, we developed an Adaptive Domain-Enhanced Transfer Learning (ADETL) framework that integrates self-supervised and continual learning strategies. This framework is adept at using incremental and unlabeled data for pre-training, in which we analyze the parameter space, loss landscape, and make the model understand the behaviour of knowledge transfer from diverse source domains. The ADETL framework improves the performance of defect classification, offering a promising solution to the challenges inherent in automatic, continuous welding operations.

Remote laser welding (RLW) technology has become a prominent joining technology in automotive industries, offering high production throughput and cost-effectiveness. Recent advancements in RLW processes such as beam oscillation have led to an increased number of input process parameters, enabling precise control over the heat input to weld metallic materials. A critical necessity in laser welding entails selecting robust process parameters that satisfy all weld quality indicators or key performance indicators (KPIs) during two stages: production stage (often implemented as robotic welding); and repair/rework stage (implemented as cobotic/manual welding to identify process parameters for weld defects) as addressing these factors in both stages is necessary to satisfy near-zero-defect strategy for some e-mobility products.. This research presents a comprehensive methodology that encompasses the following key elements: (i) the development of physics-based simulations to establish the correlation between KPIs and process parameters; (ii) the integration of a sequential modelling approach that strikes a balance between accuracy and computation time to survey the parameter space; and (iii) development of the process capability space for the quick selection of robust process parameters. Three physical phenomena are considered in the development of numerical models, which are (i) heat transfer, (ii) fluid flow and (iii) material diffusion to investigate the effect of process parameters on the weld thermal cycle, solidification parameters and solute intermixing layer during laser welding of dissimilar highstrength aluminium alloys. The governing physical phenomena are decoupled sequentially, and KPIs are estimated based on the governing phenomena. At each step, the process capability space is defined over the parameters space based on the constraints specific to the current physical phenomena. The process capability space is determined by the constraints based on the KPIs. The process capability space provides the initial combination of process parameter space during the early design stage, which satisfies all the KPIs, thus decreasing the number of experiments. The proposed methodology provides a unique capability to (i) simulate the effect of process variation as generated by the manufacturing process, (ii) model quality requirements with multiple and coupled quality requirements, and (iii) optimise process parameters under competing quality requirements.

Battery housing (BH) in modern electric vehicles must meet demanding functional requirements. The design and geometry of the BH become intricate to prevent damage during collisions and to ensure absolute impermeability to gases and water during operation. Moreover, in the pursuit of a lightweight BH, manufacturers rely on high-strength 6xxx aluminium alloys, posing significant challenges for the welding processes. It is estimated that up to 30 m of weld length is required during the construction of battery housings including joining the lid and under-shield to the main structural frame and joining the ribs to the frame for standard vehicles. Due to the increasing use of thin sheets for lightweighting the structure, thermal-induced buckling may occur and generate critical dimensional unconformities going beyond design tolerances. This underpins the need to optimise fixturing design to control thermal-induced buckling.This paper goes beyond the state-of-the-art “N-2-1″ approaches for fixturing thin and deformable parts and proposes the new principle of “unilateral N-2-1 fixturing”. The driving idea is adding unilateral restraints to the direction of thermal contraction, which ultimately causes buckling; and, keeping the direction where the thermal expansion occurs in a free state. The methodology is based on three main steps: (1) physics-based modelling of parts and fixtures using a thermo-mechanical FEA simulation; (2) calibration of the weld heat source using metallographic data; (3) validation using optical scanning technology. The methodology was demonstrated during the laser beam welding of a high-strength aluminium 6xxx thin deformable lid to a rigid high-strength 6xxx aluminium extrusion frame. Results indicated that the thermal induced buckling deformation was reduced from 15 mm, when using the state-of-the-art fixturing approach, to approximately 2 mm with the proposed methodology.

A 12-year-old boy was admitted after 11 days of fever and 2 days of nasal obstruction as well as swelling of a right cervical lymph node. Nasal endoscopy and computed tomography of the neck showed a nasopharyngeal mass occupying the entire nasopharynx, extending into the nasal cavity, and obliterating the fossa of Rosenmuller. Abdominal ultrasonography revealed a small solitary splenic abscess. Although a nasopharyngeal tumor or malignancy was initially considered, biopsy of the mass showed only suppurative granulomatous inflammation, and bacterial culture from the enlarged cervical lymph node yielded Burkholderia pseudomallei. The symptoms, nasopharyngeal mass, and cervical lymph node enlargement resolved with melioidosis-directed antibiotic therapy. Although rarely reported, the nasopharynx may be an important primary site of infection in melioidosis patients, especially in pediatric patients.

This study investigated the effect of beam oscillation on the solidification behaviour during laser welding of Al-5754 to Al-6061 alloy. In this study, a finite element model has been developed to simulate temperature and fluid flow fields by implementing different combinations of volumetric heat source models. Solidification parameters such as temperature gradient (G), solidification rate (R), cooling rate (G × R) and G/R are evaluated to understand the mechanism of microstructure formation. It was found that beam oscillation improves the tensile strength by 21.4% for full penetration welding due to an increase in the percentage of formation of equiaxed grains. Modelling results revealed that the cooling rate increases with an increase in oscillation frequency. However, tensile strength followed a parabolic distribution with a peak at the oscillation frequency of 300 Hz.

In the attempt to produce lighter battery packs at a lower cost, replacing common copper parts with aluminum components has been a popular approach in recent years. With regard to joining technologies, there is a growing interest in applying laser beam welding in battery pack manufacturing due to several advantages such as single-sided and noncontact access while maintaining a narrow heat-affected zone. Motivated by the need to control and reduce weld porosity in AA1060 battery busbar welding with the ultimate goal to enhance durability and reduce electrical resistance, this paper has been developed with the aim to studying the effect of laser beam shaping on porosity formation and, hence, generate knowledge about the underlying physics of the welding process itself. First, a multiphysics computational fluid dynamics model has been developed and calibrated to experimental data; then, the model has been deployed to study the effect of both circular and tailing beam shapes on melt pool dynamics and the evolution of porosity due to the instability of the keyhole. The study elucidated the importance of the keyhole's necking on porosity formation. Findings showed that the tail beam shapes, compared to the circular spot, have a pronounced effect on the reduction of the necking effect of the keyhole-this helps to reduce number of collapsing events of the keyhole itself, thereby leading to the reduction of porosity formation.

Background:Systemic lupus erythematosus (SLE) can involve any organ system and cause a wide range of manifestations. Noninfectious inflammatory lesions termed aseptic abscesses have been reported in some autoimmune and autoinflammatory conditions but not in childhood-onset SLE. In this report, we highlight the unusual finding of occult splenic abscesses in two children diagnosed with SLE who had no evidence of concomitant infection.Case presentation:An 8-year-old and an 11-year-old were admitted separately to the hospital with fever for 7 and 14 days, respectively. In the younger child, a generalized rash preceded the fever. Both had been well, with no significant past medical history prior to the onset of the illness. In both girls, abdominal ultrasonography showed multiple small hypoechoic lesions suggestive of abscesses scattered throughout the spleen. Their C-reactive protein and blood cultures were negative, and symptoms persisted despite intravenous antibiotics. Fulfilling the clinical and immunologic criteria for diagnosis, both were ultimately diagnosed with childhood-onset SLE. Rapid recovery of symptoms and complete resolution of the abscesses ensued with corticosteroids and immunosuppressive therapy.Conclusions:These two cases suggest that aseptic splenic abscesses may occur in childhood-onset SLE. Autoimmune conditions such as SLE should be included in the differential diagnosis of children with occult splenic abscesses.

[This corrects the article DOI: 10.1093/ofid/ofab460.].

In the present study, a finite element based numerical model is developed to evaluate heat transfer and fluid flow during the laser welding process with a moving heat source. The developed model solves the fully coupled equations of incompressible fluid flow and heat transfer. In this study, laser beam welding involving non-oscillating to oscillating beam is compared with both conditions under similar heat input per unit length i.e., same power and welding speed. Dimensionless coefficients for mass and heat transport were used to analyse the effects of Marangoni flow and thermal buoyancy. Varying combinations of radius and frequency of oscillations are studied at a constant circumferential velocity.

This paper introduced the use of an adjustable-ring-mode (ARM) laser beam to optimise the microstructure and mechanical performance of laser welded 6xxx high-strength aluminium alloy joints.A remote laser welding system equipped with transverse beam oscillation was employed and welding parameters, including the beam oscillation width and core/ring power ratio of the ARM laser beam, were investigated sequentially.Resultsshowed that the core/ring power ratio at a constant total power has a limited control on the weld geometry when integrated with beam oscillation.Increasing the beam oscillation width, up to 2.5 mm, resulted in a wider weld interface and a threshold value of 3.1 mm was determined to activate the transition from interface failure to the fusion boundary failure subjected to tensile lap shear loading, leading to a significant improvement in the joint strength from 170 N/mm to 277 N/mm.Furthermore, results revealed that proper selection of core/ring power ratio at a constant total power can restrict the formation of columnar grains near the interface between two plates, resulting in grain refinement within the weld zone.Both extremely high power ratio, for example core alone mode (infinite power ratio) and extremely low power ratio, e.g.ring alone mode (zero power ratio), lead to a low thermal gradient and cooling rate at the solidification front.A compromised solution which balances the wider formation of equiaxed dendrites and better grain refinement was determined at the power ratio of 0.33, translating to the improvement in joint strength up to 400 N/mm.

Remote Laser Welding (RLW) of Aluminium alloys has significant importance in lightweight manufacturing to decrease the weight of the body in white. It is critical to understand the physical process of transport phenomena during welding which is highly related to the mechanical performance of the joints. To investigate the underlying physics during welding and to understand the influence of beam oscillation on heat transfer, fluid flow and material mixing a transient three-dimensional Finite Element (FE) based Multiphysics model has been developed and validated from the experiments. The effect of welding speed, oscillation amplitude and oscillation frequency on the fusion zone dimensions, flow profile, vorticity profile, cooling rate and thermal gradient during the butt welding of Al-5754 to Al-6005, with sinusoidal beam oscillation, is analysed. It was found that one additional vortex is formed during beam oscillation welding due to the churning action of the oscillating beam. With the increase in oscillation amplitude, welds become wider and the depth of penetration decreases. An increase in oscillation frequency leads to an increase in the flow rate of the molten metal suggesting that the beam oscillation introduces a churning action that leads to an increase in mixing. It was highlighted that the material mixing depends on both diffusion and convection.

This research aims to explore the impact of welding process parameters and beam oscillation on weld thermal cycle during laser welding. A three-dimensional heat transfer model is developed to simulate the welding process, based on finite element method. The results obtained from the model pertaining to thermal cycle and weld morphology are in good agreement with experimental results found in the literature. The developed heat transfer model can quantify the effect of welding process parameters (i.e. heat source power, welding speed, radius of oscillation, and frequecy of oscillation) on the intermediate performance indicators (IPIs) (i.e. peak temperature, heat-affected zone (HAZ) volume, and cooling rate). Parametric contour maps for peak temperature, HAZ volume, and cooling rate are developed for the estimation of the process capability space. An integrated approach for rapid process assessment, and process capability space refinement, based on IPIs is proposed. The process capability space will guide the identification of the initial welding process parameters window and helps in reducing the number of experiments required by refining the process parameters based on the interactions with the IPIs. Among the IPIs, the peak temperature indicates the mode of welding while the HAZ volume and cooling rate represent weld quality. The regression relationship between the welding process parameters and the IPIs is established for quick estimation of IPIs to replace time-consuming numerical simulations. The application of beam oscillation widens the process capability space, making the process parameter selection more flexible due to the increase in distance from the tolerance boundaries.

Melioidosis is reported to cause a high fatality rate in children, even in the absence of risk factors for disease. The aim of this study was to identify characteristics of fatal pediatric melioidosis infection. We performed a retrospective analysis of children aged < 15 years with culture-confirmed melioidosis admitted to Bintulu Hospital in Sarawak, Malaysian Borneo, from January 2011 to December 2020. Forty-one children had culture-confirmed melioidosis. Nine (22%) had a fatal outcome; 8 (89%) had no predisposing risk factors. Bacteremia, septic shock, and acute respiratory distress syndrome were present in all fatalities. Demographic characteristics, presenting manifestation, and disseminated infection were not significantly associated with mortality, whereas the presence of splenomegaly, cytopenia, disseminated intravascular coagulation, and hepatobiliary dysfunction, all of which are features of hyperferritinemic sepsis-induced multiple-organ dysfunction syndrome, were associated with mortality. Hyperferritinemic sepsis-induced multiple-organ dysfunction syndrome may be a key component in the pathogenesis of fatal pediatric melioidosis.

BACKGROUND:Burkholderia pseudomallei, the causative agent of melioidosis, is intrinsically resistant to a broad range of antibiotics, including aminoglycosides. In Sarawak, Malaysia, a high proportion of melioidosis cases are caused by gentamicin-susceptible isolates. There are limited epidemiological and clinical data on these infections.METHODS:We conducted a retrospective study of culture-confirmed melioidosis among adults admitted to Bintulu Hospital in Sarawak, Malaysia, from January 2011 until December 2016.RESULTS:One hundred forty-eight adults with culture-confirmed melioidosis were identified. Of 129 (87%) tested, 84 (65%) had gentamicin-susceptible B pseudomallei. The average annual incidence of melioidosis was 12.3 per 100 000 population, with marked variation between districts ranging from 5.8 to 29.3 per 100 000 population. Rural districts had higher incidences of melioidosis and overwhelmingly larger proportions of gentamicin-susceptible B pseudomallei infection. Significantly more patients with gentamicin-susceptible infection had no identified risk factors, with diabetes less frequently present in this group. Ninety-eight percent had acute presentations. Pneumonia, reported in 71%, was the most common presentation. Splenic abscesses were found in 54% of those imaged. Bacteremia was present in 88%; septic shock occurred in 47%. Forty-five (35%) patients died. No differences in clinical, laboratory, or outcome characteristics were noted between gentamicin-susceptible and gentamicin-resistant infections.CONCLUSIONS:Gentamicin-susceptible B pseudomallei infections are common in Sarawak and dominate in the high-incidence rural interior regions. Clinical manifestations and outcomes are the same as for gentamicin-resistant B pseudomallei infections. Further studies are required to determine if all gentamicin-susceptible B pseudomallei infections in Sarawak are clonal and to ascertain their environmental drivers and niches.

Burkholderia pseudomallei, the causative agent of melioidosis, is intrinsically resistant to a broad range of antibiotics, including aminoglycosides. In Sarawak, Malaysia, a high proportion of melioidosis cases are caused by gentamicin-susceptible isolates. There are limited epidemiological and clinical data on these infections. Methods. We conducted a retrospective study of culture-confirmed melioidosis among adults admitted to Bintulu Hospital in Sarawak, Malaysia, from January 2011 until December 2016. One hundred forty-eight adults with culture-confirmed melioidosis were identified. Of 129 (87%) tested, 84 (65%) had gentamicin-susceptible B pseudomallei. The average annual incidence of melioidosis was 12.3 per 100 000 population, with marked variation between districts ranging from 5.8 to 29.3 per 100 000 population. Rural districts had higher incidences of melioidosis and overwhelmingly larger proportions of gentamicin-susceptible B pseudomallei infection. Significantly more patients with gentamicin-susceptible infection had no identified risk factors, with diabetes less frequently present in this group. Ninety-eight percent had acute presentations. Pneumonia, reported in 71%, was the most common presentation. Splenic abscesses were found in 54% of those imaged. Bacteremia was present in 88%; septic shock occurred in 47%. Forty-five (35%) patients died. No differences in clinical, laboratory, or outcome characteristics were noted between gentamicin-susceptible and gentamicin-resistant infections. Gentamicin-susceptible B pseudomallei infections are common in Sarawak and dominate in the high-incidence rural interior regions. Clinical manifestations and outcomes are the same as for gentamicin-resistant B pseudomallei infections. Further studies are required to determine if all gentamicin-susceptible B pseudomallei infections in Sarawak are clonal and to ascertain their environmental drivers and niches.