Multi physics modelling for a hybrid rocket engine with liquefying fuel: a sensitivity analysis on combustion instability

Hybrid rocket engines represent a promising alternative to both solid rocket motors and liquid rocket engines. They have throttling and restart capabilities with performance similar to storable liquids, but are safer and are low-cost. However, some drawbacks, such as low regression rate and combustion instability, are limiting their effective application. Paraffin-based fuels are a solution envisaged to face the low regression rate issue, and the capability to describe and predict combustion instability in the presence of liquefying fuels becomes an enabling step towards the application of hybrid rockets in next-generation space launchers. In this work, a multi physics model for hybrid rocket engines is presented and discussed. The model is based on a network of submodels, in which the chamber gas dynamics is described by a quasi-1D Euler model for reacting flows while thermal diffusion in the grain is described by the 1D heat equation in the radial direction. The need to introduce strong modelling simplifications introduces a significant uncertainty in the predictive capability of the numerical simulation. For this reason, a sensitivity analysis is performed in order to identify the key parameters which have the largest influence on combustion instability. Results are presented on a test case which refers to a paraffin-based grain burnt with hydrogen peroxide

Pain assessment in surgical patients with impaired cognition

Pain is considered the 5th vital sign and its measurement/assessment and records are required and must be systematic. Ineffective pain management involves complications in clinical status of patients, longer hospitalization times and higher costs with health. In the surgical patient with impaired cognition, hetero measurements should be made, based on behavioural and physiological indicators. We used to determine the efficacy and efficiency of the Observer Scale, the Abbey Pain Scale and Pain Assessment in Advanced Dementia (PAINAD). Our study is an applied, non-experimental, quantitative, descriptive and analytical research. The data collection instrument consisted of patients’ sociodemographic and clinical data, the Observer Scale, the Abbey Pain Scale (Rodrigues, 2013) and PAINAD (Batalha et al., 2012). We assessed pain at an early phase and 45 minutes after an intervention for its relief. The sample is non-probabilistic for convenience, consisting of 76 surgical patients with impaired cognition, admitted to the surgery services of a central hospital, aged between 38 and 96 years. There was a positive correlation between the results of the three scales, most evident in the initial evaluation. Pain intensity in the same patient is higher when assessed with PAINAD (OM = 2.16) and lower when assessed with the Observer Scale (OM = 1.78). The most effective and efficient scale is PAINAD. Due to the small sample size, we suggest confirmatory studies so that the results can be generalized

Cardiovascular risk reduction in referrals to outpatient vascular clinics

Introduction Patients with peripheral arterial disease (PAD), aneurysmal disease (AD) or carotid atherosclerosis are at high cardiovascular risk, necessitating secondary cardiovascular protection. The aim of this study was to determine compliance with cardiovascular risk reduction guidelines in new patients referred to vascular clinics. Methods A multicentre collaborative national observational audit of new patients referred to eight tertiary general vascular clinics over a three-month period in England and Wales was conducted by the Vascular and Endovascular Research Network (VERN). Referral letters, case notes and investigations were reviewed by local investigators, and data analysed by VERN. Results A total of 656 patients were included in the study: 73.2% had PAD, 23.2% had AD and 3.7% had carotid atherosclerosis. A third (37.5%) were current smokers, two-thirds (61.7%) were on antiplatelet therapy and two-thirds (61.5%) were on statin therapy. Smoking was more prevalent in the PAD cohort (PAD 41.4%, AD 27.5%, p=0.003). However, more PAD patients were on antiplatelet therapy (PAD 63.9%, AD 53.3%, p=0.024). Both antiplatelet and statin prescription significantly increased with the number of cardiovascular risk factors. Patients with a previous cardiac or cerebrovascular history were more likely to have stopped smoking, and to be on antiplatelet and statin therapy (p<0.0001 for each). Overall, 47.3% of patients were on both antiplatelet and statin therapy, and 28.9% were on antiplatelet and statin therapy and not smoking. Conclusions This study highlights deficiencies in cardiovascular risk minimisation in patients with established vascular disease. Patients with concomitant cardiac or cerebrovascular disease were more likely to be on best medical therapy

An experimental study of new rule javelins

This paper presents a comparative study of three new rule javelins (800g) used in elite competitions. Wind tunnel experiments were conducted on three commercially manufactured javelins (Hart Sports, Nordic Master 60 and Nordic Airglider) to investigate their aerodynamic characteristics. The aerodynamic drag, lift and pitching moment were measured over a range of wind speeds (25 to 33 m/s) for a range of angles of attack from 0 to 35 degree relative to the wind direction. The results suggest that the optimal release angles for each of the javelins are different due to their physical design. The angles of attack for highest lift-to-drag ratio for Hart Sports, Nordic Master 60 and Nordic Airglider javelins were found at 15°, 25° and 30° respectively. The findings of this study also indicate that Airglider javelin has better pitching moment stability than other two javelins

Early emotional, behavioural and social development of infants and young children with congenital heart disease: A systematic review

Contains fulltext : 219463.pdf (Publisher’s version ) (Closed access)The experiences of diagnosis of congenital heart disease (CHD), cardiac surgery and hospitalisation(s) are distressing and represent a significant stressor for a child and family, which may impact psychosocial development. This systematic review provides a synthesis of psychosocial outcomes of infants and young children with congenital heart disease who had cardiac surgery early in life. Twenty-eight studies related to infant and young children's psychosocial development, specifically emotional, social and behavioural functioning were identified. Variability was related to methodological factors including differences in study design, varying measurement tools and heterogeneous samples. Despite these limitations, the majority of studies were of high quality. The most common finding was a high prevalence of low-severity emotional and behavioural dysregulation. Young children with severe CHD or comorbid conditions experienced greater impairment, with higher rates of externalising behaviour problems, although internalising behaviour problems were also evident. This review integrates findings from literature in the past 28 years on the psychosocial well-being of infants and young children with CHD and demonstrates a risk for emotional, social and behavioural development difficulty, and, importantly, that symptoms of psychosocial impairment are detectable very early in infancy. We advocate for assessment and monitoring of emotional and behavioural regulation and social development to be routinely conducted from infancy to enable prevention and early intervention.18 p

An approach for the quantification of the influence of measures of risk prevention and mitigation on frequencies of rupture in piping

The paper presents a method for the quantification of the effects of measures of risk prevention or mitigation on the frequencies of rupture of pipework. Some methodologies are given in the literature to this purpose; they however assume that each plant under analysis is characterized by the same combinations of failure causes and prevention mechanisms and this assumption is not always true. The approach suggested in this paper is based on the methodology proposed by Papazoglou (1999) for the quantification of the effects of the organizational and managerial factors. Taking advantage of such methodology the objective has been achieved through the definition of the ties between the failure causes that are the origin of incidents and the measures adopted from the company in order to prevent and/or to mitigate them

Influence of Measures of Risk Prevention and Mitigation on the Frequencies of Rupture of Pipework

The paper presents a method for the quantification of the effects of measures of risk prevention or mitigation on the frequencies of rupture of pipework. Some methodologies are given in the literature to this purpose; they however assume that each plant under analysis is characterized by the same combinations of failure causes and prevention mechanisms and this assumption is not always true. The approach suggested in this paper is based on the methodology proposed by I.A.Papazoglou in 1999 for the quantification of the effects of the organizational and managerial factors. Taking advantage of such methodology the objective has been achieved through the definition of the ties between the failure causes that are the origin of incidents and the measures adopted from the company in order to prevent and/or to mitigate them. After the definition of the weights that the single failure causes can have on the incident frequencies and, on the basis of a judgement on the measures of prevention and mitigation adopted, it has been possible to proceed to the modification of the frequencies. The methodology has been applied at the most critical random events, associated to the pipework for a petrochemical plant, which have been brought back in the Safety Report of the establishment. The influence of the measures of risk prevention and mitigation on the failure causes has been discussed and defined according with the plant managemen