34 research outputs found
Experimental Analysis of Machining Parameters for EDM of AISI 4340 Steel using Copper-Tungsten Electrode
No full textEDM is a non-contact and non-conventional machining process which is used to cut conductive metals of any hardness or that are impossible or difficult to cut with conventional machining methods. The machine is also specialized in cutting complex contours that are difficult to produce using conventional cutting methods. So, this work investigated the effect of process parameters on machining of AISI 4340 steel in spark erosion process on EDM with Tungsten Copper electrode. This experimental research on EDM involves the study of the process parameters affecting the machining performance and productivity. A combined approach is used for the optimization of parameters and performance characteristics based on Taguchi method and analysis of variance (ANOVA). The design of experiments is based on Taguchi’s L16 orthogonal array. The response table and response graph for each level of machining parameters are obtained from Taguchi method to select the optimal levels of machining parameters. Main effect plot and interaction plot used to determine the optimal relationship between the various responses and parameters using MINITAB 14. It indicates which is most influencing factor or parameter. A confidence level of 95% has been taken for the analysis. Literature survey is carried out to find out the most influencing factor that affects the performance parameters. Also, literature survey gives us the various works done on EDM with other materials. In the present work, the machining parameters, namely, the pulse on time and peak current are optimized for maximum material removal rate (MRR), minimum tool wear rate (TWR) and minimum surface roughness
Video as a mediating artefact of science learning: Cogenerated views of what helps students learn from watching video
No full text© The Author(s). 2018“Doing” science in the form of practical work is one pedagogical approach to learning science alongside others such as talking science, writing science, reading science and representing science. However, scientific ideas cannot always be illustrated through practical work or field trips, therefore, different kinds of activities are needed to represent these ideas. This study focused on the power of cogenerative dialogues for teachers to learn about their students and their video preferences for learning science in a secondary science classroom. The analysis of the use of video as a mediating artefact drew on an interpretive approach framed as authentic participant-centered inquiry and employed multiple theoretical frameworks to generate perspectives on the affordances and constraints of learning from video. Through a cogenerative dialogue intervention we found that video could afford the learning of scientific ideas, however, some videographic features were distracting to students and constrained their learning. We argue that video clips as cultural artefacts are inscribed with emotion that structures students’ opportunities to engage with scientific ideas. However, to accept the authoritative information presented in videos as facts uncritically was a missed opportunity to shape students’ epistemological understanding that scientific knowledge is evidence-based and subject to critique. The implications for designing pedagogical approaches that encourage a critical stance to explore the ongoing social construction and communication of scientific ideas are discussed
The impact of self-concept and its congruence with different brands on purchase intention: Evidence from Pakistani consumers
No full textCurrent research explores the effect of self-congruity (matching one.s self with brands) on brand attitude causing purchase intention. Mostly marketers communicate the conception that their brand matches with how ideally consumers want to see themselves. So, there is an imperious self-congruity effect applied to most brands universally. This research validates the previous theories of self-congruity in Pakistani context by confirming the positive consequence of self-congruity on brand-attitude and purchase intention. Current information is highly significant for segmentation as well as branding and promotional strategies. After initial data screening, statistics from 250 respondents was analyzed by using structural equation modeling (SEM, used here after) for verification of measurement as well as structural models. The results verified the theories of self-congruity and it is recommended that better targeting is required by understanding perceived self of the target market to be used in brand communication strategies. Findings of this study revealed that consumers evaluate brands by matching them with their perceived self (self-image) and accordingly develops attitude towards brands which ultimately influences their purchase intention i.e. those brands are preferred which matches with one.s perceived self-image. Findings also confirmed that Self-Congruity (the perception about one.s self) effects the consumer.s choice to prefer a particular brand (which matches to their perceived self) in the form of brand attitude which ultimately determines purchase intention. This understanding could be further used to improve segmentation and targeting decisions
Efficacy and Safety of Concomitant Tricuspid Repair in Patients Undergoing Mitral Valve Surgery: a Systematic Review and Meta-Analysis.
No full textTricuspid valve repair (TVR) is recommended for patients with moderate primary tricuspid regurgitation (TR), those with moderate TR, and a history of heart failure without annular dilation, while being essential for patients with severe secondary TR undergoing MVS. The meta-analysis aimed to evaluate the efficacy and safety of tricuspid valve repair in patients undergoing MVS. We systematically searched PubMed, Embase, and Google Scholar through January 2022, and studies comparing patients with TVR and those without TVR were selected. The primary outcomes were 30-day, and all-cause mortality. In this meta-analysis, 20 studies were included with a patient population of 72,422. No significant differences were observed between patients undergoing TVR with MVS, in comparison to MVS group only for the primary outcomes i.e., 30-day mortality (RR: 1.14, 95% CI [0.69, 1.87], and all-cause mortality (RR: 1.16, 95% CI [0.86, 1.57]. From the secondary outcomes, pacemaker insertion (RR: 2.62, 95% CI [2.24, 3.06]), new-onset TR or progression (RR: 0.32, 95% CI [0.16, 0.66]), stroke (RR: 1.22, 95% CI [1.05, 1.42]), cross-clamp time (WMD: 17.67, 95% CI [13.96, 21.37]), surgery time (WMD: 43.59, 95% CI [37.07, 50.10]), ICU time (WMD: 19.50, 95% CI [9.31, 29.67]), and ventilation time (WMD: 6.62, 95% CI [0.69, 12.55]) were significant. However, major bleeding events, atrial fibrillation, renal failure, heart failure hospitalization, postoperative MI, wound infection, early or prolonged morbidity, cardiopulmonary bypass time, and duration of hospital stay were non-significant. Our meta-analysis has furthered the discussion for weighing the risks and benefits of pursuing TVR during MVS
An Agent-Based Optimization Framework for Engineered Complex Adaptive Systems with Application to Demand Response in Electricity Markets
No full textabstract: The main objective of this research is to develop an integrated method to study emergent behavior and consequences of evolution and adaptation in engineered complex adaptive systems (ECASs). A multi-layer conceptual framework and modeling approach including behavioral and structural aspects is provided to describe the structure of a class of engineered complex systems and predict their future adaptive patterns. The approach allows the examination of complexity in the structure and the behavior of components as a result of their connections and in relation to their environment. This research describes and uses the major differences of natural complex adaptive systems (CASs) with artificial/engineered CASs to build a framework and platform for ECAS. While this framework focuses on the critical factors of an engineered system, it also enables one to synthetically employ engineering and mathematical models to analyze and measure complexity in such systems. In this way concepts of complex systems science are adapted to management science and system of systems engineering. In particular an integrated consumer-based optimization and agent-based modeling (ABM) platform is presented that enables managers to predict and partially control patterns of behaviors in ECASs. Demonstrated on the U.S. electricity markets, ABM is integrated with normative and subjective decision behavior recommended by the U.S. Department of Energy (DOE) and Federal Energy Regulatory Commission (FERC). The approach integrates social networks, social science, complexity theory, and diffusion theory. Furthermore, it has unique and significant contribution in exploring and representing concrete managerial insights for ECASs and offering new optimized actions and modeling paradigms in agent-based simulation.Dissertation/ThesisPh.D. Industrial Engineering 201
Trends in Alzheimer's disease and heart failure-related mortality among older American adults: Insights from the CDC WONDER database
No full textIntroduction: Alzheimer's disease is one of the leading causes of death among the elderly in the United States with heart failure sharing similar risk factors. This study investigated trends and disparities in Alzheimer's disease mortality among older adults with heart failure from 1999 to 2020 in the United States. Methods: Making use of ICD-10 codes death certificate data from the Centers for Disease Control and Prevention Wide-Ranging OnLine Data for Epidemiologic Research database was retrieved for patients aged ≥65 years between 1999 and 2020. Age-adjusted mortality rates (AAMRs), per 100,000 people, and Annual Percentage Change (APCs) with their respective 95 % Confidence Intervals (CI) were also calculated. Data was stratified by year, gender, race and geographical distribution. Results: Alzheimer's disease with coexisting heart failure was responsible for 192,459 deaths between 1999 and 2020. Overall the AAMR increased from 21.32 in 1999 to 24.56 in 2005 (APC: 1.9760*; 95 % CI: 0.6001 to 3.9507) after which a significant decrease to 16.52 by 2013 was observed (APC: −4.9301*; 95 % CI: −6.5209 to −4.0119). AAMRs decreased from this point forward reaching 22.21 in 2020 (APC: 4.1573*; 95 % CI: 3.0373 to 5.7232). Women had higher AAMRs than men (21.57 vs 18.41). Among racial groups, the Non-Hispanic (NH) White (21.62) population had the highest AAMRs followed by NH Black/African American (17.87), Hispanic/Latino (14.3) and NH Asian/Pacific Islander (8.96). Furthermore, AAMRs also varied by census region (West: 24.05; Midwest: 22.83; South: 21.1; Northeast: 13.38). Moreover, nonmetropolitan areas had higher AAMRs compared to metropolitan areas (27.23 vs 19.09). States in the top 90th percentile such as Kentucky, Oklahoma, Washington, North Dakota and Mississippi had AAMRs that were three times higher relative to states in the lower 10th percentile including Nevada, Florida, New York, District of Columbia and Hawaii. Conclusion: Alzheimer's disease mortality with associated heart failure has shown considerable variation in adults ≥65 years. AAMRs were highest in women, NH Whites, residents of the West and nonmetropolitan patient populations. Targeted interventions and a more holistic approach to patient management are essential in achieving favorable outcomes for vulnerable groups moving forward
Sex-related disparities in incidence and in-hospital outcomes of Atrial fibrillation complicated by non-ST-elevation myocardial infarction from the national in-sample database (2016\u20132022)
No full textCauses and Determinants of Heart Failure Readmissions Post Transcutaneous Aortic Valve Replacement: A Systematic Review and Meta-Analysis
No full textSafety and efficacy of colchicine in COVID-19 patients: A systematic review and meta-analysis of randomized control trials
No full textBackground: Colchicine has been used an effective anti-inflammatory drug to treat gout diseases. Owing to its pharmacodynamic of inhibiting interleukins, it has been repurposed to target the cytokine storm post-SARS-CoV-2 invasion. The goal of this meta-analysis was to evaluate the safety profile of colchicine in COVID-19 patients using the gold-standard randomised-control trials.
Methods: Electronic databases (Pubmed, Google Scholar, and Cochrane) were systematically searched until June 2021 and RCTs were extracted. Outcomes of interest included all-cause mortality, COVID-19 severity, mechanical ventilation, C-reactive protein and D-dimer levels. Using a random-effects model, dichotomous outcomes were pooled using odds ratios (OR) through the generic inverse variance formula while weighted mean differences were calculated using the Wan\u27s method. P-values \u3c 0.05 were considered statistically significant for all outcomes.
Results: A total population of 16,048 from five RCTs were included in the analysis. Of this, 7957 were randomized to colchicine, and 8091 received standard care, with an average age of 60.67 years. Colchicine was observed to significantly reduce COVID-19 severity (OR: 0.41, 95% CI [0.22, 0.76]; p = 0.005), and CRP levels (WMD: -19.99, 95% CI [-32.09, -7.89]; p = 0.001). However, there was no significant difference in D-dimer levels (WMD: 0.31, 95% CI [-0.61, 1.23]; p = 0.51), mechanical ventilation (OR: 0.42, 95% CI [0.17, 1.03]; p = 0.06; I2 = 74%) and all-cause mortality (OR: 0.98, 95% CI [0.83, 1.16]; p = 0.84) among patients receiving colchicine or standard care.
Conclusion: Colchicine treatment decreased CRP levels and COVID-19 severity, with dimer levels, all-cause mortality and mechanical ventilation remaining seemingly unaffected. Thus, clinical trials need to be carried out that allow effective evaluation of colchicine in COVID-19 patients
Causes and Predictors of Heart Failure Hospitalizations Following Transcatheter Aortic Valve Implantation: A Systematic Review and Meta-Analysis.
No full textBACKGROUND: Transcutaneous aortic valve implantation (TAVI) has transformed the management of aortic stenosis (AS) and is increasingly being used for patients with symptomatic, severe aortic stenosis who are ineligible or at high risk for conventional cardiac surgery.
METHODS: PUBMED, Google Scholar, and SCOPUS databases were searched to identify studies reporting heart failure hospitalization after TAVI. Major factors evaluated for HF hospitalization were age, comorbidities such as hypertension, atrial fibrillation (AF), chronic pulmonary disease including COPD, chronic kidney disease, baseline LVEF before the procedure, NYHA symptom class, and society of thoracic surgeons (STS) score. Hazard ratio (HR) with a 95% confidence interval were computed using random-effects models.
RESULTS: A total of eight studies were included comprising 77,745 patients who underwent TAVI for severe aortic stenosis. The presence of diabetes mellitus (HR: 1.39, 95% CI [1.17, 1.66], chronic kidney disease (CKD) (HR: 1.39, 95% CI [1.31, 1.48], atrial fibrillation (HR: 1.69, 95% CI [1.42, 2.01], chronic pulmonary disease (HR: 1.33, 95% CI [1.12, 1.58], and a high STS score (HR: 1.07, 95% CI [1.03, 1.11] were positive predictors of 1-year HF hospitalization after TAVI.
CONCLUSION: Patients with diabetes mellitus, AF, CKD, chronic pulmonary disease, and a high STS score are at an increased risk of heart failure hospitalization at 1-year of TAVI, whereas increasing age, hypertension, LVE
