Tool wear in dry helical milling for hole-making in AISI H13 hardened steel

Helical milling is a hole-making process which can be applied to achieve high-quality finished boreholes in hardened steels. Due to the drilling process limitations, which are intensified when applied in hardened steels, the helical milling process can be applied on hole-making tasks in moulds and dies industry, since milling have been widely applied in moulds and dies machining to replace high-cost operations like grinding and electrical discharge machining. However, to succeed in achieving high-quality boreholes in hardened parts, which presents high added value due to previous operations, tool wear in the helical milling of hardened steels should be more investigated. In the present study, dry helical milling tool life tests were conducted in AISI H13 hardened steel parts, varying the cutting velocity. The flank wear on frontal cutting edges was progressively measured through optical microscopy, and SEM/EDS was performed in frontal and peripheral worn cutting edges. The wear occurred progressively in the flank of the frontal cutting edges with adhesion and oxidation as main wear mechanisms. In the peripheral edges, coating loss, and adhesion of workpiece material in the tool clearance surface were observed, besides fracture in the tool nose flank with the highest cutting velocity. A nested ANOVA was performed to evaluate the burr height in the borehole exit. The tool life stage was statistically significant in the burr height.publishe

Large-scale unit commitment under uncertainty: an updated literature survey

The Unit Commitment problem in energy management aims at finding the optimal production schedule of a set of generation units, while meeting various system-wide constraints. It has always been a large-scale, non-convex, difficult problem, especially in view of the fact that, due to operational requirements, it has to be solved in an unreasonably small time for its size. Recently, growing renewable energy shares have strongly increased the level of uncertainty in the system, making the (ideal) Unit Commitment model a large-scale, non-convex and uncertain (stochastic, robust, chance-constrained) program. We provide a survey of the literature on methods for the Uncertain Unit Commitment problem, in all its variants. We start with a review of the main contributions on solution methods for the deterministic versions of the problem, focussing on those based on mathematical programming techniques that are more relevant for the uncertain versions of the problem. We then present and categorize the approaches to the latter, while providing entry points to the relevant literature on optimization under uncertainty. This is an updated version of the paper "Large-scale Unit Commitment under uncertainty: a literature survey" that appeared in 4OR 13(2), 115--171 (2015); this version has over 170 more citations, most of which appeared in the last three years, proving how fast the literature on uncertain Unit Commitment evolves, and therefore the interest in this subject

Patients’ preferences for coronary revascularization: a systematic review

Carlos Alberto da Silva Magliano,1 Andrea Libório Monteiro,2 Amanda Rebeca de Oliveira Rebelo,1 Claudia Cristina de Aguiar Pereira31Instituto Nacional de Cardiologia, INC, Rio de Janeiro, Brazil; 2Department of Pharmacy Systems, Outcomes and Policy, College of Pharmacy, University of Illinois at Chicago, Illinois, USA; 3Escola Nacional de Saúde Pública, ENSP, FIOCRUZ, Rio de Janeiro, BrazilAims: Guidelines current recommendations regarding the best treatment option for coronary revascularization are usually based on composite outcomes that were not selected or weighed with patients thence they may fail in representing patients’ preferences adequately. This systematic review aimed to appraise existing literature surrounding stated preference (SP) regarding coronary revascularization.Methods and results: Studies related to SP regarding coronary revascularization were searched on Medline, Embase and Lilacs databases. Two reviewers screened all titles independently, and consensus resolved any disagreements. Of 735 total citations, six studies were included and qualitatively synthesized. Notably, the attributes most often cited in these studies coincided with those already used in clinical trials (death, myocardial infarction, stroke and redo revascularization). Half of the studies analyzed the use of composite endpoints and showed the necessity to review this practice since the attributes are weighed differently, and there is a disagreement between patients and physicians. Also, a large variety of methods were used to elicitate and value the attributes such as rating, ranking, standard gamble, willingness to pay, and discrete choice experiments.Conclusion: Despite a large number of studies comparing revascularization treatment efficacy, there are just a few focusing on patients’ preferences. The selection of outcomes to be considered in the trade-off between treatment options and how to weigh them properly, taking into consideration patients’ preferences, need to be explored in future trials.Keywords: review, systematic, preference, patient, angioplasty, transluminal, percutaneous coronary, bypass surgery, coronary revascularizatio

Patient and physician preferences for attributes of coronary revascularization

Carlos Alberto da Silva Magliano,1 Andrea Liborio Monteiro,2 Bernardo Rangel Tura,1 Claudia Silvia Rocha Oliveira,1 Amanda Rebeca de Oliveira Rebelo,1 Claudia Cristina de Aguiar Pereira3 1HTA Department, National Institute of Cardiology, Rio de Janeiro, Brazil; 2Department of Pharmacy Systems, Outcomes and Policy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA; 3The National School of Public Health Sergio Arouca ENSP/Fiocruz, Rio de Janeiro, Brazil Background: Patients with a diagnosis of coronary artery disease (CAD) may face important decisions regarding treatment options, with the “right choice” depending on the relative weights of risks and benefits. Studies performed as discrete choice experiments are used to estimate these weights, and attribute selection is an essential step in the design of these studies. Attributes not included in the design cannot be analyzed. In this study, we aimed to elicit, rank, and rate attributes that may be considered important to patients and physicians who must choose between angioplasty and surgery for coronary revascularization. Methods: The elicitation process involved performing a systematic review to search for attributes cited in declared preference studies in addition to face-to-face interviews with cardiologists and experts. The interviews were audio-recorded in digital format, and the collected data were transcribed and searched to identify new attributes. The criterion used to finish the data collection process was sampling saturation. Results: A systematic review resulted in the selection of the following 14 attributes: atrial fibrillation, heart failure, incision scar, length of stay, long-term survival, myocardial infarction, periprocedural death, postoperative infection, postprocedural angina, pseudoaneurysm, renal failure, repeat coronary artery bypass grafting, repeat percutaneous coronary intervention, and stroke. The interviews added no new attributes. After rating, we identified significant differences in the values that patients and cardiologists placed on renal insufficiency (p<0.001), periprocedural death (p<0.001), and long-term survival (p<0.001). Conclusion: Decisions regarding the best treatment option for patients with CAD should be made based on differences in risk and the patient’s preference regarding the most relevant endpoints. We elicited, ranked, and rated 14 attributes related to CAD treatment options. This list of attributes may help researchers who seek to perform future preference studies of CAD treatment options. Keywords: preference, ranking, rating, coronary, angin

Feasibility of visual aids for risk evaluation by hospitalized patients with coronary artery disease: results from face-to-face interviews

Carlos Alberto da Silva Magliano,1 Andrea Liborio Monteiro,2 Bernardo Rangel Tura,1 Claudia Silvia Rocha Oliveira,1 Amanda Rebeca de Oliveira Rebelo,1 Claudia Cristina de Aguiar Pereira3 1NATS, Instituto Nacional de Cardiologia, INC, Rio de Janeiro, Rio de Janeiro, Brazil; 2Department of Pharmacy Systems, Outcomes and Policy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA; 3Escola Nacional de Saúde Pública, ENSP, FIOCRUZ, Rio de Janeiro, Brazil Purpose: Communicating information about risk and probability to patients is considered a difficult task. In this study, we aim to evaluate the use of visual aids representing perioperative mortality and long-term survival in the communication process for patients diagnosed with coronary artery disease at the National Institute of Cardiology, a Brazilian public hospital specializing in cardiology. Patients and methods: One-on-one interviews were conducted between August 1 and November 20, 2017. Patients were asked to imagine that their doctor was seeking their input in the decision regarding which treatment represented the best option for them. Patients were required to choose between alternatives by considering only the different benefits and risks shown in each scenario, described as the proportion of patients who had died during the perioperative period and within 5 years. Each participant evaluated the same eight scenarios. We evaluated their answers in a qualitative and quantitative analysis. Results: The main findings were that all patients verbally expressed concern about perioperative mortality and that 25% did not express concern about long-term mortality. Twelve percent considered the probabilities irrelevant on the grounds that their prognosis would depend on “God’s will.” Ten percent of the patients disregarded the reported likelihood of perioperative mortality, deciding to focus solely on the “chance of being cured.” In the quantitative analysis, the vast majority of respondents chose the “correct” alternatives, meaning that they made consistent and rational choices. Conclusion: The use of visual aids to present risk attributes appeared feasible in our sample. The impact of heuristics and religious beliefs on shared health decision making needs to be explored better in future studies. Keywords: patients’ preferences, coronary revascularization, angina, cardiology, coronary artery bypass grafting, percutaneous coronary interventio