Študija učinkovitosti rezanja plastike, ojačene z ogljikovimi vlakni, z abrazivnim vodnim curkom

In recent years, composite materials such as carbon-fibre-reinforced plastic (CFRP) have been widely used in medical devices, industries, marine and aerospace applications due to their high resistance-to-weight ratio toughness, corrosion resistance, and other novel properties. The machining of these composite materials using conventional machines results in poor precision and surface finishing due to excess heat generation at the tool-material contact zone. The drawbacks of the conventional machining process can be overcome with the adoption of a novel cutting technique using pressurized water, which can dissipate the heat generated by the impact of abrasive particles against the material in order to eliminate the poor precision and surface finishing caused by overheating. In this experimental study, the performance of surface quality (roughness and kerf angle) of CFRP machining using an abrasive water jet technique has been studied for a wide range of cutting parameters, such as water pressure and cutting speed

Development and validation of a score to predict postoperative respiratory failure in a multicentre European cohort : A prospective, observational study

BACKGROUND Postoperative respiratory failure (PRF) is the most frequent respiratory complication following surgery. OBJECTIVE The objective of this study was to build a clinically useful predictive model for the development of PRF. DESIGN A prospective observational study of a multicentre cohort. SETTING Sixty-three hospitals across Europe. PATIENTS Patients undergoing any surgical procedure under general or regional anaesthesia during 7-day recruitment periods. MAIN OUTCOME MEASURES Development of PRF within 5 days of surgery. PRF was defined by a partial pressure of oxygen in arterial blood (PaO2) less than 8 kPa or new onset oxyhaemoglobin saturation measured by pulse oximetry (SpO(2)) less than 90% whilst breathing room air that required conventional oxygen therapy, noninvasive or invasive mechanical ventilation. RESULTS PRF developed in 224 patients (4.2% of the 5384 patients studied). In-hospital mortality [95% confidence interval (95% CI)] was higher in patients who developed PRF [10.3% (6.3 to 14.3) vs. 0.4% (0.2 to 0.6)]. Regression modelling identified a predictive PRF score that includes seven independent risk factors: low preoperative SpO(2); at least one preoperative respiratory symptom; preoperative chronic liver disease; history of congestive heart failure; open intrathoracic or upper abdominal surgery; surgical procedure lasting at least 2 h; and emergency surgery. The area under the receiver operating characteristic curve (c-statistic) was 0.82 (95% CI 0.79 to 0.85) and the Hosmer-Lemeshow goodness-of-fit statistic was 7.08 (P = 0.253). CONCLUSION A risk score based on seven objective, easily assessed factors was able to predict which patients would develop PRF. The score could potentially facilitate preoperative risk assessment and management and provide a basis for testing interventions to improve outcomes. The study was registered at ClinicalTrials.gov (identifier NCT01346709)