High effectiveness liquid droplet/gas heat exchanger for space power applications

A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approx. 100 to 300 micron diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber. The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9 to 0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Bryaton cycle is discussed to illustrate the performance and operational characteristics of this heat exchanger concept

Investigation of the aerothermodynamics of hypervelocity reacting flows in the ram accelerator

New diagnostic techniques for measuring the high pressure flow fields associated with high velocity ram accelerator propulsive modes was experimentally investigated. Individual propulsive modes are distinguished by their operating Mach number range and the manner in which the combustion process is initiated and stabilized. Operation of the thermally choked ram accelerator mode begins by injecting the projectile into the accelerator tube at a prescribed entrance velocity by means of a conventional light gas gun. A specially designed obturator, which is used to seal the bore of the gun, plays a key role in the ignition of the propellant gases in the subsonic combustion mode of the ram accelerator. Once ignited, the combustion process travels with the projectile and releases enough heat to thermally choke the flow within several tube diameters behind it, thereby stabilizing a high pressure zone on the rear of the projectile. When the accelerating projectile approaches the Chapman-Jouguet detonation speed of the propellant mixture, the combustion region is observed to move up onto the afterbody of the projectile as the pressure field evolves to a distinctively different form that implies the presence of supersonic combustion processes. Eventually, a high enough Mach number is reached that the ram effect is sufficient to cause the combustion process to occur entirely on the body. Propulsive cycles utilizing on-body heat release can be established either by continuously accelerating the projectile in a single propellant mixture from low initial in-tube Mach numbers (M less than 4) or by injecting the projectile at a speed above the propellant's Chapman-Jouguet detonation speed. The results of experimental and theoretical explorations of ram accelerator gas dynamic phenomena and the effectiveness of the new diagnostic techniques are presented in this report

Investigation of advanced propulsion technologies: The RAM accelerator and the flowing gas radiation heater

The two principal areas of advanced propulsion investigated are the ram accelerator and the flowing gas radiation heater. The concept of the ram accelerator is presented as a hypervelocity launcher for large-scale aeroballistic range applications in hypersonics and aerothermodynamics research. The ram accelerator is an in-bore ramjet device in which a projectile shaped like the centerbody of a supersonic ramjet is propelled in a stationary tube filled with a tailored combustible gas mixture. Combustion on and behind the projectile generates thrust which accelerates it to very high velocities. The acceleration can be tailored for the 'soft launch' of instrumented models. The distinctive reacting flow phenomena that have been observed in the ram accelerator are relevant to the aerothermodynamic processes in airbreathing hypersonic propulsion systems and are useful for validating sophisticated CFD codes. The recently demonstrated scalability of the device and the ability to control the rate of acceleration offer unique opportunities for the use of the ram accelerator as a large-scale hypersonic ground test facility. The flowing gas radiation receiver is a novel concept for using solar energy to heat a working fluid for space power or propulsion. Focused solar radiation is absorbed directly in a working gas, rather than by heat transfer through a solid surface. Previous theoretical analysis had demonstrated that radiation trapping reduces energy loss compared to that of blackbody receivers, and enables higher efficiencies and higher peak temperatures. An experiment was carried out to measure the temperature profile of an infrared-active gas and demonstrate the effect of radiation trapping. The success of this effort validates analytical models of heat transfer in this receiver, and confirms the potential of this approach for achieving high efficiency space power and propulsion

High Efficiency Energy Conversion Systems for Liquid Nitrogen Automobiles

This investigation of the use of cryogens as energy storage media for zero emission vehicles has found that using liquid nitrogen to liquefy the working fluids of one or more closed Rankine power cycles can be an effective means for increasing motive power. System configurations are presented which can realize a specific energy greater than 400 kJ/kg-LN2 (110 W-hr/kg-LN2) without relying on isothermal expanders. A zero emission vehicle utilizing such a propulsion system would have an energy storage reservoir that can be refilled in a matter of minutes and a range comparable to that of a conventional automobile

Combating escalating harms associated with pharmaceutical opioid use in Australia: The POPPY II study protocol

© Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. Introduction Opioid prescribing has increased 15-fold in Australia in the past two decades, alongside increases in a range of opioid-related harms such as opioid dependence and overdose. However, despite concerns about increasing opioid use, extramedical use and harms, there is a lack of population-level evidence about the drivers of long-term prescribed opioid use, dependence, overdose and other harms. Methods and analysis We will form a cohort of all adult residents in New South Wales (NSW), Australia, who initiated prescribed opioids from 2002 using Pharmaceutical Benefits Scheme dispensing records. This cohort will be linked to a wide range of other datasets containing information on sociodemographic and clinical characteristics, health service use and adverse outcomes (eg, opioid dependence and non-fatal and fatal overdose). Analyses will initially examine patterns and predictors of prescribed opioid use and then apply regression and survival analysis to quantify the risks and risk factors of adverse outcomes associated with prescribed opioid use. Ethics and dissemination This study has received full ethical approval from the Australian Institute of Health and Welfare Ethics Committee, the NSW Population and Health Services Research Committee and the ACT Health Human Research Ethics Committee. This will be the largest postmarketing surveillance study of prescribed opioids undertaken in Australia, linking exposure and outcomes and examining risk factors for adverse outcomes of prescribed opioids. As such, this work has important translational promise, with direct relevance to regulatory authorities and agencies worldwide. Project findings will be disseminated at scientific conferences and in peer-reviewed journals. We will also conduct targeted dissemination with policy makers, professional bodies and peak bodies in the pain, medicine and addiction fields through stakeholder workshops and advisory groups. Results will be reported in accordance with the REporting of studies Conducted using Observational Routinely collected Data (RECORD) Statement

A multi-centre audit to assess the effectiveness of the British Orthodontic Society 'Hold that Smile' retainer videos

Introduction: Retention is a crucial part of orthodontic treatment, however patients often do not wear their retainers as advised. The British Orthodontic Society developed the ‘Hold that Smile’ campaign in 2017, to improve patient knowledge about retention. Information is provided in two formats: a cartoon and a conventional film. / Objective: To assess if patients find the ‘Hold that Smile’ videos useful, and if they improved patients’ intended retainer wear. The gold standard was that 90% of patients should intend to wear their retainers long-term following watching the videos. / Design: National multi-centre audit. / Setting: Nine units in the UK. / Methods: Patients 10 years old and over, in fixed appliances or retention, watched the retainer videos and then completed a questionnaire that was designed specifically for this audit. Each unit collected data for approximately 30 patients. / Results: Data was collected for 278 patients in total. The average age was 17.9 years; 64.4% of patients were female and 35.6% male. Most patients (86.3%) watched both videos and, of these, 44.1% preferred the film, 31.3% preferred the cartoon and 24.6% had no preference. The majority of patients (81.3%) felt that the film provided them with new information, compared with a lower percentage (48.5%) for the cartoon and more patients said they would recommend the film (76.3%) compared with the cartoon (63.3%). Prior to watching the videos, 77.0% of patients felt they knew about long-term retainer wear and 74.3% of those intended to wear their retainers long-term. After watching the videos, 96.4% of all patients thought they would now wear their retainers long-term. / Conclusion: After watching the videos, there was a notable increase in the number of patients planning to wear their retainers long-term and the gold standard was met. Therefore, these videos may be beneficial in improving understanding and compliance with retention

Age at first alcohol-related hospital separation or emergency department presentation and rate of re-admission: A retrospective data linkage cohort of young Australians

Introduction: Alcohol is a leading risk factor for death and disease in young people. We compare age-specific characteristics of young people who experience their first (‘index’) alcohol-related hospitalisation or emergency department (ED) presentation, and whether age at index predicts 12-month rates of readmission. Methods: We used a retrospective linked-data cohort of 10,300 people aged 12–20 years with an index alcohol-related hospital and/or ED record in New South Wales, Australia from 2005 to 2013. Age group (early adolescent [12–14 years], late adolescent [15–17 years], young adult [18–20 years]) and diagnosis fields were used in logistic regression analyses and to calculate incidence rates with adjustment for year of index event, sex, socioeconomic disadvantage and residence remoteness. Results: People who experienced their index event in early adolescence (adjusted relative risk ratio [ARRR] 0.45 [95% confidence interval 0.39, 0.52]) or late adolescence (ARRR 0.82 [0.74, 0.90]) were less likely to be male compared to young adults. Early adolescents (ARRR 0.60 [0.51, 0.70]) and late adolescents (ARRR 0.84 [0.76, 0.93]) were less likely to have a hospitalisation index event. Early adolescents (adjusted incidence rate ratio 1.40 [1.15, 1.71]) and late adolescents (adjusted incidence rate ratio 1.16 [1.01, 1.34]) were more likely than young adults to have a subsequent 12-month non-poisoning injury ED presentation. Discussion and Conclusions: We identified preventable hospital events in young people who have previously experienced an alcohol-related ED presentation or hospitalisation, with age-specific characteristics and outcomes that can be used to inform future health policy and service planning

Constraints and affordances for UK doctors-in-training to exercise agency: A dialogical analysis

This is the final version. Available on open access from Wiley via the DOI in this recordData availability statement: Data sharing is not applicable to this article as no new data were created or analyzed in this study.INTRODUCTION: The goal of medical education is to develop clinicians who have sufficient agency (capacity to act) to practise effectively in clinical workplaces and to learn from work throughout their careers. Little research has focused on experiences of organisational structures and the role of these in constraining or affording agency. The aim of this study was to identify priorities for organisational change, by identifying and analysing key moments of agency described by doctors-in-training. METHODS: This was a secondary qualitative analysis of data from a large national mixed methods research programme, which examined the work and wellbeing of UK doctors-in-training. Using a dialogical approach, we identified 56 key moments of agency within the transcripts of 22 semi-structured interviews with doctors based across the UK in their first year after graduation. By analysing action within the key moments from a sociocultural theoretical perspective, we identified tangible changes that healthcare organisations can make to afford agency. RESULTS: When talking about team working, participants gave specific descriptions of agency (or lack thereof) and used adversarial metaphors, but when talking about the wider healthcare system, their dialogue was disengaged and they appeared resigned to having no agency to shape the agenda. Organisational changes that could afford greater agency to doctors-in-training were improving induction, smoothing peaks and troughs of responsibility and providing a means of timely feedback on patient care. CONCLUSIONS: Our findings identified some organisational changes needed for doctors-in-training to practise effectively and learn from work. The findings also highlight a need to improve workplace-based team dynamics and empower trainees to influence policy. By targeting change, healthcare organisations can better support doctors-in-training, which will ultimately benefit patients.General Medical Counci

A comparison of course-related stressors in undergraduate problem-based learning (PBL) versus non-PBL medical programmes

Background: Medical students report high levels of stress related to their medical training as well as to other personal and financial factors. The aim of this study is to investigate whether there are differences in course-related stressors reported by medical students on undergraduate problem-based learning (PBL) and non-PBL programmes in the UK. Method: A cross-sectional study of second-year medical students in two UK medical schools (one PBL and one non-PBL programme) was conducted. A 16-question self-report questionnaire, derived from the Perceived Medical Student Stress Scale and the Higher Education Stress Inventory, was used to measure course-related stressors. Following univariate analysis of each stressor between groups, multivariate logistic regression was used to determine which stressors were the best predictors of each course type, while controlling for socio-demographic differences between the groups. Results: A total of 280 students responded. Compared to the non-PBL students (N = 197), the PBL students (N = 83) were significantly more likely to agree that: they did not know what the faculty expected of them (Odds Ratio (OR) = 0.38, p = 0.03); there were too many small group sessions facilitated only by students resulting in an unclear curriculum (OR = 0.04, p < 0.0001); and that there was a lack of opportunity to explore academic subjects of interest (OR = 0.40, p = 0.02). They were significantly more likely to disagree that: there was a lack of encouragement from teachers (OR = 3.11, p = 0.02); and that the medical course fostered a sense of anonymity and feelings of isolation amongst students (OR = 3.42, p = 0.008). Conclusion: There are significant differences in the perceived course-related stressors affecting medical students on PBL and non-PBL programmes. Course designers and student support services should therefore tailor their work to minimise, or help students cope with, the specific stressors on each course type to ensure optimum learning and wellbeing among our future doctors