Numerical investigation of inlet starting methods for axisymmetric scramjet engines

Hypersonic airbreathing propulsion, in particular, scramjets (supersonic combustion ramjets), is a promising technology that offers great potential for efficient and economical access-to-space and atmospheric transport. Reliable in-flight inlet starting is of critical importance for the successful operation of scramjet engines, particularly internal-compression configurations with high-contraction inlets. A wide variety of methods including diaphragm rupture and sliding doors (diaphragm erosion) have been contrived in order to address the inlet starting issue, which is inherent to hypersonic airbreathing systems with internal compression. This paper discusses the mechanism and causes of inlet unstart from aerodynamic viewpoints and assesses the effectiveness and viability of various starting methods, based on steady and transient simulations by means of high-fidelity computational fluid dynamics

Numerical investigation of turbulence effects on boundary layer separation in axisymmetric scramjet inlets via design optimisation

Inlet aerodynamics plays a key role in the successful operation of hypersonic airbreathing systems for flexible and economical access-to-space and atmospheric flight. Flow separation, however, can critically deteriorate the engine performance particularly for internal-compression scramjets with high contraction, where the boundary layer is susceptible to adverse pressure gradients. The flow physics of an axisymmetric scramjet inlet is investigated by means of the design optimisation of transition trip wires

Numerical investigation into the combustion behavior of an inlet-fueled thermal-compression-like scramjet

A numerical study on the combustion behavior of an inlet-fueled three-dimensional nonuniform-compression scramjet is presented. This paper is an extension to previous work on the combustion processes in a premixed three-dimensional nonuniform-compression scramjet, where thermal compression was shown to enhance combustion. This paper demonstrates how thermal compression can be used in a generic scramjet configuration with a realistic fuel-injection method to enhance performance at high flight Mach numbers. Such a scramjet offers an extra degree of freedom in the design process of fixed-geometry scramjets that must operate over a range of flight Mach numbers. In this study, how the combustion processes are affected is investigated, with the added realism of inlet porthole fuel injection. Ignition is established from within a shock-induced boundary-layer separation at the entrance to the combustor. Radicals that form upstream of the combustor within the inlet, from the injection method, enhance combustion. Coupling of the inlet-induced spanwise gradients and thermal compression improves combustion. The results highlight that, although the fuel-injection method imparts local changes to the flow structures, the global flow behavior does not change compared to previous premixed results. This combustion behavior will be reproduced when using other fueling methods that deliver partially premixed fuel and air to the combustor entrance

Impact craters on Venus: An overview from Magellan observations

Magellan has revealed an ensemble of impact craters on Venus that is unique in many important ways. We have compiled a database describing 842 craters on 89 percent of the planet's surface mapped through orbit 2578 (the craters range in diameter from 1.5 to 280 km). We have studied the distribution, size-frequency, morphology, and geology of these craters both in aggregate and, for some craters, in more detail. We have found the following: (1) the spatial distribution of craters is highly uniform; (2) the size-density distribution of craters with diameters greater than or equal to 35 km is consistent with a 'production' population having a surprisingly young age of about 0.5 Ga (based on the estimated population of Venus-crossing asteroids); (3) the spectrum of crater modification differs greatly from that on other planets--62 percent of all craters are pristine, only 4 percent volcanically embayed, and the remainder affected by tectonism, but none are severely and progressively depleted based on size-density distribution extrapolated from larger craters; (4) large craters have a progression of morphologies generally similar to those on other planets, but small craters are typically irregular or multiple rather than bowl shaped; (5) diffuse radar-bright or -dark features surround some craters, and about 370 similar diffuse 'splotches' with no central crater are observed whose size-density distribution is similar to that of small craters; and (6) other features unique to Venus include radar-bright or -dark parabolic arcs opening westward and extensive outflows originating in crater ejecta

Are people who participate in cultural activities more satisfied with life?

The influence of various aspects of life on wellbeing has been extensively researched. However, despite little empirical evidence, participation in leisure activities has been assumed to increase subjective wellbeing. Leisure is important because it is more under personal control than other sources of life satisfaction. This study asked whether people who participate in cultural leisure activities have higher life satisfaction than people who do not, if different types of leisure have the same influence on life satisfaction and if satisfaction is dependent on the frequency of participation or the number of activities undertaken. It used data from UKHLS Survey to establish associations between type, number and frequency of participation in leisure activities and life satisfaction. Results showed an independent and positive association of participation in sport, heritage and active-creative leisure activities and life satisfaction but not for participation in popular entertainment, theatre hobbies and museum/galleries. The association of reading hobbies and sedentary-creative activities and life satisfaction was negative. High life satisfaction was associated with engaging in a number of different activities rather than the frequency of participation in each of them. The results have implications for policy makers and leisure services providers, in particular those associated with heritage recreation. Subjective wellbeing measures, such as life satisfaction, and not economic measures alone should be considered in the evaluation of services. The promotion of leisure activities which are active and promote social interaction should be considered in programmes aimed at improving the quality of life

Magnetism, FeS colloids, and Origins of Life

A number of features of living systems: reversible interactions and weak bonds underlying motor-dynamics; gel-sol transitions; cellular connected fractal organization; asymmetry in interactions and organization; quantum coherent phenomena; to name some, can have a natural accounting via $physical$ interactions, which we therefore seek to incorporate by expanding the horizons of `chemistry-only' approaches to the origins of life. It is suggested that the magnetic 'face' of the minerals from the inorganic world, recognized to have played a pivotal role in initiating Life, may throw light on some of these issues. A magnetic environment in the form of rocks in the Hadean Ocean could have enabled the accretion and therefore an ordered confinement of super-paramagnetic colloids within a structured phase. A moderate H-field can help magnetic nano-particles to not only overcome thermal fluctuations but also harness them. Such controlled dynamics brings in the possibility of accessing quantum effects, which together with frustrations in magnetic ordering and hysteresis (a natural mechanism for a primitive memory) could throw light on the birth of biological information which, as Abel argues, requires a combination of order and complexity. This scenario gains strength from observations of scale-free framboidal forms of the greigite mineral, with a magnetic basis of assembly. And greigite's metabolic potential plays a key role in the mound scenario of Russell and coworkers-an expansion of which is suggested for including magnetism.Comment: 42 pages, 5 figures, to be published in A.R. Memorial volume, Ed Krishnaswami Alladi, Springer 201

CRTAP Is Required for Prolyl 3- Hydroxylation and Mutations Cause Recessive Osteogenesis Imperfecta

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Keyboard Contamination in Intensive Care Unit: Is Cleaning Enough? Prospective Research of In Situ Effectiveness of a Tea Tree Oil (KTEO) Film

After the SARS-CoV-2 pandemic, disinfection practices and microbial load reduction have become even more important and rigorous. To determine the contamination of keyboard surface and the relative risk to transfer healthcare-associated pathogens to susceptible patients, as it frequently happens in Intensive Care Unit (ICU), a standard keyboard (SK), a cleanable keyless keyboard (KK) with smooth surface and a standard keyboard coated with a 3M Tegaderm film added with active essential oil (tea tree oil) (KTEO) were tested. S. aureus, including MRSA strains, were detected in ICU, with values ranging from 15% to 57%. Gram negative strains belonging to the Enterobacteriaceae family were also found with values ranging from 14% to 71%. Similar Gram positive and Gram negative strains were found on all surfaces, but with low percentage, and only environmental bacteria were detected using the settling plates method. The Microbial Challenge Test performed on KTEO showed high rates of decrease for all the pathogens with statistical significance both at 24 and 48h (p=0.003* and p=0.040*, respectively). Our results suggest that the use of KTEO may be a feasible strategy for reducing the transmission of pathogens in health care setting and may be complementary to surface cleaning protocols