Hybrid Taguchi-GRA-CRITIC Optimization Method for Multi-Response Optimization of Micro-EDM Drilling Process Parameters

In this study, an attempt is made to investigate how the operational parameters such as capacitance, voltage, feed rate, and rotating speed affect the material removal rate, tool wear, overcut, and taper angle for micro-EDM drilling of aluminium 6061 utilizing brass C360 electrode. A novel Taguchi-GRA-CRITIC hybrid optimization methodology is used to obtain the optimal combination of micro-EDM drilling process parameters. The experiment was designed using the Taguchi L18 orthogonal array, and responses were recorded for each experiment. Grey Relational Analysis (GRA) is applied to improve the multi-response of the planned experiment. The weighting values corresponding to various responses are determined using CRITIC (criterion importance through intercriteria correlation) analysis. The hybrid methodology determines the best combination of process parameters for different responses. ANOVA was used to discover the most critical parameters. Finally, confirmation experiments were conducted with optimal parameters to identify improvement in grey relational grade over the initial parameters. The study\u27s findings indicate that, compared to the initial process parameter setting, the grey relational grade (GRG) increased by 92.36% with the optimal parameter setting

Determination of Fracture Parameters for Multiple Cracks of Laminated Composite Finite Plate

A predictive method for estimation of stress state at zone of crack tip and assessment of remaining component lifetime depend on the stress intensity factor (SIF). This paper discusses the numerical approach for prediction of first ply failure load (F-L), progressive failure load, SIF and critical SIF for multiple cracks configurations of laminated composite finite plate using finite element method (FEM). The Hashin and Chang failure criterion are incorporated in ABAQUS using subroutine approach user defined field variables (USDFLD) for prediction of progressive fracture response of laminated composite finite plate, which is not directly available in the software. A tensile experiment on laminated composite finite plate with stress concentration is performed to validate the numerically predicted subroutine results, shows excellent agreement. The typical results are presented to examine effect of changing the crack tip distance (S), crack offset distance (H), and stacking fiber angle (theta) on F-L, and SIF

Hybrid Taguchi-GRA-CRITIC Optimization Method for Multi-Response Optimization of Micro-EDM Drilling Process Parameters

In this study, an attempt is made to investigate how the operational parameters such as capacitance, voltage, feed rate, and rotating speed affect the material removal rate, tool wear, overcut, and taper angle for micro-EDM drilling of aluminium 6061 utilizing brass C360 electrode. A novel Taguchi-GRA-CRITIC hybrid optimization methodology is used to obtain the optimal combination of micro-EDM drilling process parameters. The experiment was designed using the Taguchi L18 orthogonal array, and responses were recorded for each experiment. Grey Relational Analysis (GRA) is applied to improve the multi-response of the planned experiment. The weighting values corresponding to various responses are determined using CRITIC (criterion importance through intercriteria correlation) analysis. The hybrid methodology determines the best combination of process parameters for different responses. ANOVA was used to discover the most critical parameters. Finally, confirmation experiments were conducted with optimal parameters to identify improvement in grey relational grade over the initial parameters. The study's findings indicate that, compared to the initial process parameter setting, the grey relational grade (GRG) increased by 92.36% with the optimal parameter setting

COVID-19 infected ST-Elevation myocardial infarction in India (COSTA INDIA)

Objective: To find out differences in the presentation, management and outcomes of COVID-19 infected STEMI patients compared to age and sex-matched non-infected STEMI patients treated during the same period. Methods: This was a retrospective multicentre observational registry in which we collected data of COVID-19 positive STEMI patients from selected tertiary care hospitals across India. For every COVID-19 positive STEMI patient, two age and sex-matched COVID-19 negative STEMI patients were enrolled as control. The primary endpoint was a composite of in-hospital mortality, re-infarction, heart failure, and stroke. Results: 410 COVID-19 positive STEMI cases were compared with 799 COVID-19 negative STEMI cases. The composite of death/reinfarction/stroke/heart failure was significantly higher among the COVID-19 positive STEMI patients compared with COVID-19 negative STEMI cases (27.1% vs 20.7% p value = 0.01); though mortality rate did not differ significantly (8.0% vs 5.8% p value = 0.13). Significantly lower proportion of COVID-19 positive STEMI patients received reperfusion treatment and primary PCI (60.7% vs 71.1% p value=< 0.001 and 15.4% vs 23.4% p value = 0.001 respectively). Rate of systematic early PCI (pharmaco-invasive treatment) was significantly lower in the COVID-19 positive group compared with COVID-19 negative group. There was no difference in the prevalence of high thrombus burden (14.5% and 12.0% p value = 0.55 among COVID-19 positive and negative patients respectively) Conclusions: In this large registry of STEMI patients, we did not find significant excess in in-hospital mortality among COVID-19 co-infected patients compared with non-infected patients despite lower rate of primary PCI and reperfusion treatment, though composite of in-hospital mortality, re-infarction, stroke and heart failure was higher

Impact of COVID-19 on heart failure hospitalization and outcome in India – A cardiological society of India study (CSI–HF in COVID 19 times study – “The COVID C–HF study”)

Objectives: The presentation and outcomes of acute decompensated heart failure (ADHF) during COVID times (June 2020 to Dec 2020) were compared with the historical control during the same period in 2019. Methods: Data of 4806 consecutive patients of acute HF admitted in 22 centres in the country were collected during this period. The admission patterns, aetiology, outcomes, prescription of guideline-directed medical therapy (GDMT) and interventions were analysed in this retrospective study. Results: Admissions for acute heart failure during the pandemic period in 2020 decreased by 20% compared to the corresponding six-month period in 2019, with numbers dropping from 2675 to 2131. However, no difference in the epidemiology was seen. The mean age of presentation in 2019 was 61.75 (±13.7) years, and 59.97 (±14.6) years in 2020. There was a significant decrease in the mean age of presentation (p = 0.001). Also. the proportion of male patients decreased significantly from 68.67% to 65.84% (p = 0.037). The in-hospital mortality for acute heart failure did not differ significantly between 2019 and 2020 (4.19% and 4.,97%) respectively (p = 0.19). The proportion of patients with HFrEF did not change in 2020 compared to 2019 (76.82% vs 75.74%, respectively). The average duration of hospital stay was 6.5 days. Conclusion: The outcomes of ADHF patients admitted during the Covid pandemic did not differ significantly. The length of hospital stay remained the same. The study highlighted the sub-optimal use of GDMT, though slightly improving over the last few years

Search for intermediate mass black hole binaries in the first observing run of Advanced LIGO

International audienceDuring their first observational run, the two Advanced LIGO detectors attained an unprecedented sensitivity, resulting in the first direct detections of gravitational-wave signals produced by stellar-mass binary black hole systems. This paper reports on an all-sky search for gravitational waves (GWs) from merging intermediate mass black hole binaries (IMBHBs). The combined results from two independent search techniques were used in this study: the first employs a matched-filter algorithm that uses a bank of filters covering the GW signal parameter space, while the second is a generic search for GW transients (bursts). No GWs from IMBHBs were detected; therefore, we constrain the rate of several classes of IMBHB mergers. The most stringent limit is obtained for black holes of individual mass 100  M⊙, with spins aligned with the binary orbital angular momentum. For such systems, the merger rate is constrained to be less than 0.93  Gpc−3 yr−1 in comoving units at the 90% confidence level, an improvement of nearly 2 orders of magnitude over previous upper limits

First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data

International audienceWe report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the first Advanced LIGO observing run. This search investigates the low frequency range of Advanced LIGO data, between 20 and 100 Hz, much of which was not explored in initial LIGO. The search was made possible by the computing power provided by the volunteers of the Einstein@Home project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population, corresponding to a sensitivity depth of 48.7  [1/Hz]. At the frequency of best strain sensitivity, near 100 Hz, we set 90% confidence upper limits of 1.8×10-25. At the low end of our frequency range, 20 Hz, we achieve upper limits of 3.9×10-24. At 55 Hz we can exclude sources with ellipticities greater than 10-5 within 100 pc of Earth with fiducial value of the principal moment of inertia of 1038  kg m2

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

International audienceSpinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far

Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo

International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M⊙, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M⊙ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M⊙ and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]† Deceased, August 2020