An investigation of combustion instability in aircraft-engine reheat systems

The principal objective of this study was to examine experimentally the effects of upstream temperature, velocity, gutter blockage, tailpipe length, and main and pilot fuel flows, on the form of combustion instability encountered in aircraft reheat systems which is sometimes referred to as 'buzz'. Tests were carried out at atmospheric pressure for upstream temperatures of between 200 and 500°C, and upstream velocities ranging from 140 to 200 ft/sec. Three values of stabilizer blockage were employed, namely 25, 30 and 35%. The tailpipe length was varied between 9 and 45 inches. Auto-correlation techniques were used in the frequency analysis of the buzz waveforms. It was found that a certain minimum tailpipe length is necessary in order to produce buzz which is then strengthened as the tailpipe length is increased. Buzz also becomes more pronounced with an increase in gas velocity but stabilizer blockage appears to have no discernible effect … [cont.]

The Long and Winding Road: Archiving and Re-Using Qualitative Data from 12 Research Projects Spanning 16 Years

We describe a pilot project designed to assess the feasibility of re-use across 12 diverse qualitative datasets related to Human Immunodeficiency Virus (HIV) in the UK, from research projects undertaken between 1997 and 2013 – an approach which is chronically underused. First, we consider the sweeping biomedical changes and imperatives relating to HIV in this time frame, offering a rationale for data re-use at this point in the epidemic. We then reflexively situate the processes and procedures we devised for this study with reference to relevant methodological literature. Hammersley’s and Leonelli’s contributions have been particularly instructive through this process, and following their lead, we conclude with further considerations for those undertaking qualitative data re-use, reflecting on the extent to which qualitative data re-use as a practice requires attention to both the given and the constructed aspects of data when assembled as evidence

Foreword to APPG Policy Report: The Missing Link: HIV and mental health

Cite as: APPG on HIV and Aids (2020) APPG Policy Report: The Missing Link: HIV and mental health

The relentless spread of tuberculosis in Zambia - trends over the past 37 years (1964- 2000)

Objective. To review trends in the rates of tuberculosis (TB) case notifications over a 37-year period.Design. A retrospective study of Ministry of Health records on TB notifications between 1 January 1964 and 31 December 2000.Setting. Zambia, sub-Saharan Africa.Methods. Retrospective analysis of case-notification data for TB of the Zambia Ministry of Health annual returns.Outcome measures. Annual TB case-notification rates and trends over the past 37 years.Results. TB case-notification data from 1964 to 2000 show a 12-fold increase over the past two decades, and apparent gains in controlling TB seen in the 1960s and 1970s have been reversed over the past two decades. A stable situation during the period 1964 - 1984 (case-notification rate remained around 100 per 100 000 population) was followed by an exponential increase since the mid-1980s. The absolute number of new TBcases increased from 8 246 in 1985 (124/100 000) to 38 863 (409/100 000) in 1996 and 52 000 (512/100 000) in 2000. Comparison of case-notification rates over the past 2 decades with neighbouring countries (Zimbabwe, Malawi and Tanzania) show that Zambia has one of the highest case notification rates in the region.Conclusions. Zambia, like many countries in Africa, is in the midst of a serious TB epidemic and there are no signs that it is abating. This increase was most likely due to the impact of the HIV / AIDS epidemic and subsequent breakdown of TB services. Concerted donor-government efforts should invest appropriately in long-term plans for TB control

Two-dimensional plasma expansion in a magnetic nozzle: Separation due to electron inertia

A previous axisymmetric model of the supersonic expansion of a collisionless, hot plasma in a divergent magnetic nozzle is extended here in order to include electron-inertia effects. Up to dominant order on all components of the electron velocity, electron momentum equations still reduce to three conservation laws. Electron inertia leads to outward electron separation from the magnetic streamtubes. The progressive plasma filling of the adjacent vacuum region is consistent with electron-inertia being part of finite electron Larmor radius effects, which increase downstream and eventually demagnetize the plasma. Current ambipolarity is not fulfilled and ion separation can be either outwards or inwards of magnetic streamtubes, depending on their magnetization. Electron separation penalizes slightly the plume efficiency and is larger for plasma beams injected with large pressure gradients. An alternative nonzero electron-inertia model [E. Hooper, J. Propul. Power 9, 757 (1993)] based on cold plasmas and current ambipolarity, which predicts inwards electron separation, is discussed critically. A possible competition of the gyroviscous force with electron-inertia effects is commented briefly

The gaming involvement and informal learning framework

Aim. This article presents a model of how gaming involvement and informal learning come together in practice. Method. Based on a series of interviews, case studies, and a wider survey, the Gaming Involvement and Informal Learning (GIIL) framework indicates how involvement with a variety of gaming practices can lead to a range of different learning experiences. Results. The framework is able to account for both how and what people learn from gaming while also highlighting the influence of player identity. Further, the iterative relationship between identity, involvement, and learning is emphasized: The more strongly someone identifies themselves as a gamer, the greater their micro- and macro-level involvement and the more likely they are to learn from their gaming experiences. Conclusion. The implications of the findings are discussed with regard to informal and formal learning

Teaching introductory undergraduate Physics using commercial video games

Commercial video games are increasingly using sophisticated physics simulations to create a more immersive experience for players. This also makes them a powerful tool for engaging students in learning physics. We provide some examples to show how commercial off-the-shelf games can be used to teach specific topics in introductory undergraduate physics. The examples are selected from a course taught predominantly through the medium of commercial video games.Comment: Accepted to Physics Education, Fig1 does not render properly in this versio

Risk related to pre–diabetes mellitus and diabetes mellitus in heart failure with reduced ejection fraction: insights from prospective comparison of ARNI with ACEI to determine impact on global mortality and morbidity in heart failure trial

Background—The prevalence of pre–diabetes mellitus and its consequences in patients with heart failure and reduced ejection fraction are not known. We investigated these in the Prospective Comparison of ARNI With ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGM-HF) trial. Methods and Results—We examined clinical outcomes in 8399 patients with heart failure and reduced ejection fraction according to history of diabetes mellitus and glycemic status (baseline hemoglobin A1c [HbA1c]: <6.0% [<42 mmol/mol], 6.0%–6.4% [42–47 mmol/mol; pre–diabetes mellitus], and ≥6.5% [≥48 mmol/mol; diabetes mellitus]), in Cox regression models adjusted for known predictors of poor outcome. Patients with a history of diabetes mellitus (n=2907 [35%]) had a higher risk of the primary composite outcome of heart failure hospitalization or cardiovascular mortality compared with those without a history of diabetes mellitus: adjusted hazard ratio, 1.38; 95% confidence interval, 1.25 to 1.52;P<0.001. HbA1c measurement showed that an additional 1106 (13% of total) patients had undiagnosed diabetes mellitus and 2103 (25%) had pre–diabetes mellitus. The hazard ratio for patients with undiagnosed diabetes mellitus (HbA1c, >6.5%) and known diabetes mellitus compared with those with HbA1c<6.0% was 1.39 (1.17–1.64); P<0.001 and 1.64 (1.43–1.87); P<0.001, respectively. Patients with pre–diabetes mellitus were also at higher risk (hazard ratio, 1.27 [1.10–1.47];P<0.001) compared with those with HbA1c<6.0%. The benefit of LCZ696 (sacubitril/valsartan) compared with enalapril was consistent across the range of HbA1c in the trial. Conclusions—In patients with heart failure and reduced ejection fraction, dysglycemia is common and pre–diabetes mellitus is associated with a higher risk of adverse cardiovascular outcomes (compared with patients with no diabetes mellitus and HbA1c <6.0%). LCZ696 was beneficial compared with enalapril, irrespective of glycemic status

Naturally Rehearsing Passwords

We introduce quantitative usability and security models to guide the design of password management schemes --- systematic strategies to help users create and remember multiple passwords. In the same way that security proofs in cryptography are based on complexity-theoretic assumptions (e.g., hardness of factoring and discrete logarithm), we quantify usability by introducing usability assumptions. In particular, password management relies on assumptions about human memory, e.g., that a user who follows a particular rehearsal schedule will successfully maintain the corresponding memory. These assumptions are informed by research in cognitive science and validated through empirical studies. Given rehearsal requirements and a user's visitation schedule for each account, we use the total number of extra rehearsals that the user would have to do to remember all of his passwords as a measure of the usability of the password scheme. Our usability model leads us to a key observation: password reuse benefits users not only by reducing the number of passwords that the user has to memorize, but more importantly by increasing the natural rehearsal rate for each password. We also present a security model which accounts for the complexity of password management with multiple accounts and associated threats, including online, offline, and plaintext password leak attacks. Observing that current password management schemes are either insecure or unusable, we present Shared Cues--- a new scheme in which the underlying secret is strategically shared across accounts to ensure that most rehearsal requirements are satisfied naturally while simultaneously providing strong security. The construction uses the Chinese Remainder Theorem to achieve these competing goals

Ten Years After: An ‘Austerity Audit’ of Services and Living Conditions for People Living with HIV in the UK, a Decade after the Financial Crisis

Cite as: HIV Psychosocial Network (2018). Ten Years After: An ‘Austerity Audit’ of Services and Living Conditions for People Living with HIV in the UK, a Decade after the Financial Crisis