Modelling Machining-induced Residual Stresses after Laser-assisted Turning of Steels

Abstract. The current study examines the effects of laser assistance on machining-induced residual stresses (RS), using finite element modelling, during turning of AISI 4340 steel at different feed rates. Dry orthogonal cutting was modelled, along with the pre-heating effect of the laser beam. Laser-assisted machining (LAM) resulted in higher surface tensile RS compared to conventional machining, with more pronounced effects at lower feed rates. This is basically because the assisted material experienced higher plastic deformation, due to thermal softening, as well as higher temperatures, which are both attributed to the pre-heating effect of LAM

A Proposed ANN-Based Acceleration Control Scheme for Soft Starting Induction Motor

In this article, a new soft starting control scheme based on an artificial neural network (ANN) is presented for a three-phase induction motor (IM) drive system. The main task of the control scheme is to keep the accelerating torque constant at a level based on the value of reference acceleration. This is accomplished by the proper choice of the firing angles of thyristors in the soft starter. Using the ANN approach, the complexity of the online determination of the thyristors firing angles is resolved. The IM torque-speed characteristic curves are firstly used to train the ANN model. Secondly, the IM- soft starter system is modeled using MATLAB/SIMULINK. To prove the effectiveness of the proposed ANN-based acceleration control scheme, different reference accelerations and loading conditions are applied and investigated. Finally, a laboratory prototype of 3 kW soft starter is implemented. The proposed control scheme is executed in a real-time environment using a digital signal processor (Model: TMS320F28335). The simulation and real-time results significantly confirm that the proposed controller can efficiently reduce the IM starting current and torque pulsations. This in turn ensures a smooth acceleration of the IM during the starting process. Moreover, the proposed control scheme has the superiority over several soft starting control schemes since it has a simple control circuit configuration, less required sensors, and low computational burden of the control algorithm. © 2021 Institute of Electrical and Electronics Engineers Inc.. All rights reserved

MicroRNA-150 down Regulation in Acute Myeloid Leukaemia Patients and Its Prognostic Implication

BACKGROUND: MicroRNAs (miRNAs) are small, non-coding RNAs that are important for post-transcriptional gene regulation in both healthy and morbid conditions. Numerous miRNAs promote tumorigenesis, while others have a tumour suppressive effects. Acute myeloid leukaemia (AML) is a heterogeneous group of genetically diverse hematopoietic malignancies with variable response to treatment. AIM: Our study aimed to investigate the possible role of miR-150 in de novo adult AML and the impact of its level on survival, and we used in the silicon analysis to predict the main target genes involved in miR-150 mediated cancer pathway. MATERIAL AND METHODS: We evaluated miR-150 expression profiling assay using TaqMan primer probes RT-PCR in the plasma of 50 adult AML patients, before the start of treatment and at day 28 of treatment, along with 20 normal adult control samples. miR-16 was used as an endogenous reference for standardisation. Follow-up of patients during treatment at day 28 of induction chemotherapy and after one year was done. RESULTS: In this study, we found a significantly lower level of miR-150 in AML patients when compared to controls (p = 0.005) with 0.62 fold change than in healthy controls. Patients were divided into two groups: the low miR-150 group (miR-150 < 1) and the high miR-150 group (miR-150 > 1). A statistically significant difference was found between the two groups regarding initial total leukocytic count and initial PB blast count while for the TLC, HB and PLT count at follow up. No difference in the overall survival between the low and the high miR-150 groups could be demonstrated. CONCLUSION: Our results suggest that miR-150 functions as a tumour suppressor and gatekeeper in inhibiting cell transformation and that its downregulation is required for leukemogenesis

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Dynamic analysis with optimum trajectory planning of multiple degree-of-freedom surgical micro-robot

The present work aims to analyze kinematics and dynamics accompanied with an optimum trajectory planning, of a multiple degree-of-freedom positioning surgical micro-robot. The kinematic model was developed using Denavit–Hartenberg algorithm, while dynamic model was developed using Lagrange technique. The trajectory optimization was implemented using different local, global and hybrid optimization techniques. For local optimization, “Fmincon” was employed. Genetic Algorithm (GA), Pattern Search (PS), and Particle Swarm (PSO) were utilized as global optimization techniques. In hybrid optimization approach, GA was used for global optimization while PS was utilized as a local optimization technique for further results refinement. Polynomials of sixth order and fourth order were assumed during all trajectory optimization approaches. The objective function was assumed to minimize the total consumed energy by the positioning manipulator. Non-optimized analysis was investigated as well, using several conventional trajectory planning techniques including fifth order polynomial, third order polynomial, cycloidal formula and elliptical formula. The angle of rotation for all joints ranged from zero to one and half radian, and the motion duration was five seconds for all the presented results. MATLAB codes were created for simulation and optimization processes. Keywords: Micro-robot, Optimal trajectory, Dynamic analysis, Kinematic analysis, Genetic algorithm, Particle swarm, Pattern search, Hybrid optimizatio

Modelling Machining-induced Residual Stresses after Laser-assisted Turning of Steels

Abstract. The current study examines the effects of laser assistance on machining-induced residual stresses (RS), using finite element modelling, during turning of AISI 4340 steel at different feed rates. Dry orthogonal cutting was modelled, along with the pre-heating effect of the laser beam. Laser-assisted machining (LAM) resulted in higher surface tensile RS compared to conventional machining, with more pronounced effects at lower feed rates. This is basically because the assisted material experienced higher plastic deformation, due to thermal softening, as well as higher temperatures, which are both attributed to the pre-heating effect of LAM

Investigating the effect of augmenting the anti-roll-bar with a torsional-dynamic-absorber on the handling-stability and the ride-comfort of the off-road-vehicles

Enhancing the handling and ride comfort is the main objective in the off-road vehicles.Ride dynamics studies. To augment the control authority on the handling and the ride comfort for such vehicles, a soft suspension system should exist. The main drawback of the soft suspension is the high probability of rolling-over especially in sudden maneuver cases. Anti-roll bar is a classical mechanical linkage that has been used to increase the rolling stiffness without affecting the vertical stiffness of the vehicle. The main drawback of the antiroll bar is the increase of the load transfer between the vehicle sides and increases the rolling acceleration, which negatively affects the ride comfort. In the current study, we investigate the effect of adding torsional dynamic absorber beside the antiroll bar on improving the handling and the ride comfort of the vehicle. More over the structural integrity of this kind of vehicles is expected to be maintained for longer service life compared with the same vehicles without the torsional dynamic absorber. A model of 4 DOF vibrating system that represent the suspension system of the half rear of the off-road vehicle is adopted and the mathematical model is derived. The frequency responses of the model were studied statistically as well as the time domain response. The results reveal that, to a large extent, the augmented antiroll suspension system succeeded to damp the system quickly and reducing all vibration frequency levels. The simulation results show that the vehicle rolling settling time has been reduced by 30% approximately. Also the rolling acceleration mean value among the resonance band in the frequency response curve was reduced by 60%

On the Role of Damage Evolution in Finite Element Modeling of the Cutting Process and Sensing Residual Stresses

This study focuses on the role of the damage evolution when estimating the failure behavior of AISI 1045 steel for sensing and measuring metal cutting parameters. A total of five Lagrangian explicit models are established to investigate the effect of applying damage evolution techniques. The Johnson–Cook failure model is introduced once to fully represent damage behavior, i.e., no damage evolution is considered, and as a damage initiation criterion in the remaining approaches. A fracture energy-based model is included to model damage propagation with different evolution rates. Temperature-dependent and temperature-independent fracture energy models are also investigated. Dry orthogonal cutting and residual stresses measurements of AISI 1045 are conducted for validation. The significance of the damage evolution is investigated using honed-tool and sharp-tool models. Including the damage evolution led to a prediction of higher workpiece temperatures, plastic strains, cutting forces, and residual stresses, with no clear differences between linear and exponential evolution rates. The role of damage evolution is more evident when temperature-dependent evolution models are used

Genetic Basis of Combining Ability for Various Quantitative Traits Using CMS Lines of Rice (Oryza sativa L.)

Line × Tester experiment was carried out at the Experimental Farm of Rice Research and Training Center (RRTC), Sakha, Kafrelsheikh, Egypt during three growing seasons to evaluate the performance of 21 F1 hybrids along with their parents. Three cytoplasmic male sterile lines, two wild abortive (Wild Abortive); IR69625A, IR70368A and one (Kalinga) K17A as female were tested with seven cultivars/lines as testers. The analysis of variance detected that, highly significant variations among genotypes (parental lines with their crosses) for all traits in both seasons and in their combined analysis. Two hybrid combinations; IR69625A×Giza178 and IR69625A×Giza179 were recorded the best values for grain yield under both seasons and their combined. General combining ability (GCA) and specific combining ability (SCA) effects of genotypes for the studied traits were estimated. The results indicated that, K17A (female) and Giza 179 (male) were the best combiner for early heading date and could be useful to breed early maturing rice cultivars. The CMS line IR69625A and Giza178, Giza179 gave highly significant and positive GCA value and so appeared to be good parental lines combiner in hybrid combinations for high grain yield/plant. The positive values of GCA mean increased for grain yield/plant, which could be useful in breeding programs for high yield potential rice cultivars. The hybrid combination IR69625A×Giza179 showed highly significant and positive SCA estimates under both seasons and their combined. In conclusion, it is clear that this hybrid seemed promising hybrid for earliness and high grain yield under Egyptian conditions

Development of an in-house COVID-19 serology ELISA Test

Background: COVID-19 pandemic created an unprecedented demand for reagents and diagnostic tools to confirm COVID-19 cases. Thus, the development of a robust in-house diagnostic test is considered of high importance. Within a few days after exposure, the human body produces specific antibodies that recognize the surface proteins of the invading SARS-CoV-2 virus 1 . Therefore, virus specific immunoglobulins are neutralizing antibodies and their appearance in the blood is a good sign of immunity 2 . The aim of this study was to develop an in-house COVID-19 serology ELISA test to quantify induced antibody responses. This test can help identify convalescent plasma donors with high antibody titers that can be used to treat other patients. Methods: Spike protein antigen is highly expressed in SARS-CoV-2 3 . Recombinant protein corresponding to the spike receptor-binding domain (RBD), which binds to specific antibodies circulating in COVID-19 patients' blood was used as the antigen in this colorimetric ELISA test. Briefly, a 96-microtiter well plate was coated with RBD protein, where serum dilutions were added. Antibody titers were detected using an anti-human IgG- peroxidase labelled antibody and the substrate o-phenylenediamine dihydrochloride; measured at optical density (OD) of 450 nm (Figure 1). Results: The in-house quantitative serology test was validated using serum samples collected from severe COVID-19 patients (n = 282) admitted to the intensive care unit at Hamad General Hospital. Serum samples from non-COVID-19 (n = 10) were used as a negative control. We detected high antibody titers in ~90% of COVID-19 sera. In contrast, no SARS-CoV-2 specific antibodies were detected in the serum of non-infected subjects (n = 6), pooled human serum collected before 2019, or Middle East Respiratory Syndrome (MERS) infected subjects (n = 3) confirming the specificity and the sensitivity of this in-house serology test. Conclusion: This in-house quantitative serology test is sensitive, specific, and inexpensive. The test can address the rising issue of COVID-19 supply chain globally and foster the capacity-building efforts envisioned by Qatar University.qscienc