On the transonic aerodynamics of a compressor blade row

Linearized analyses have been carried out for the induced velocity and pressure fields within a compressor blade row operating in an infinite annulus at transonic Mach numbers of the flow relative to the blades. In addition, the relationship between the induced velocity and the shape of the mean blade surface has been determined. A computational scheme has been developed for evaluating the blade mean surface ordinates and surface pressure distributions. The separation of the effects of a specified blade thickness distribution from the effects of a specified distribution of the blade lift has been established. In this way, blade mean surface shapes that are necessary for the blades to be locally nonlifting have been computed and are presented for two examples of blades with biconvex parabolic arc sections of radially tapering thickness. Blade shapes that are required to achieve a zero thickness, uniform chordwise loading, constant work spanwise loading are also presented for two examples. In addition, corresponding surface pressure distributions are given. The flow relative to the blade tips has a high subsonic Mach number in the examples that have been computed. The results suggest that at near-sonic relative tip speeds the effective blade shape is dominated by the thickness distribution, with the lift distribution playing only a minor role

Similarity of nuclear structure in 132Sn and 208Pb regions: proton-neutron multiplets

Starting from the striking similarity of proton-neutron multiplets in 134Sb and 210Bi, we perform a shell-model study of nuclei with two additional protons or neutrons to find out to what extent this analogy persists. We employ effective interactions derived from the CD-Bonn nucleon-nucleon potential renormalized by use of the V-low-k approach. The calculated results for 136Sb, 212Bi, 136I, and 212At are in very good agreement with the available experimental data. The similarity between 132Sn and 208Pb regions is discussed in connection with the effective interaction, emphasizing the role of core polarization effects.Comment: 4 pages, 3 figures, 2 table

On the magnetospheric ULF wave counterpart of substorm onset

One near‐ubiquitous signature of substorms observed on the ground is the azimuthal structuring of the onset auroral arc in the minutes prior to onset. Termed auroral beads, these optical signatures correspond to concurrent exponential increases in ground ultralow frequency (ULF) wave power and are likely the result of a plasma instability in the magnetosphere. Here, we present a case study showing the development of auroral beads from a Time History of Events and Macroscale Interactions during Substorms (THEMIS) all‐sky camera with near simultaneous exponential increases in auroral brightness, ionospheric and conjugate magnetotail ULF wave power, evidencing their intrinsic link. We further present a survey of magnetic field fluctuations in the magnetotail around substorm onset. We find remarkably similar superposed epoch analyses of ULF power around substorm onset from space and conjugate ionospheric observations. Examining periods of exponential wave growth, we find the ground‐ and space‐based observations to be consistent, with average growth rates of ∼0.01 s−1, lasting for ∼4 min. Cross‐correlation suggests that the space‐based observations lead those on the ground by approximately 1–1.5 min. Meanwhile, spacecraft located premidnight and ∼10 RE downtail are more likely to observe enhanced wave power. These combined observations lead us to conclude that there is a magnetospheric counterpart of auroral beads and exponentially increasing ground ULF wave power. This is likely the result of the linear phase of a magnetospheric instability, active in the magnetotail for several minutes prior to auroral breakup

From reflective learning to reflective practice: assessing transfer

A key attribute of reflective practice is its capacity for on-going purposeful learning in relation to changing and demanding professional work. The teaching of reflective learning techniques in management education is intended to promote deep-level learning and the application of critical thinking to oneself, personal experience and the work environment. However, we lack empirical evidence that the teaching of reflective learning leads to enhanced reflective practice in professional work. This study provides an examination of reflection in work post formal education. It reports on interviews with 18 Human Resource professionals. Reflection does not get ‘left behind’ on completion of formal teaching but there is not an even or simple process of transfer to a work context. Likewise, there was not a slavish adherence to reflective techniques but rather some evidence that students were able to translate their learning into something meaningful for their practice. © 2016 Society for Research into Higher Educatio

Striving to Practice What We Preach: Academics reflecting on teaching reflective practice

That reflection is part of the HRD academics’ continuing professional development is a powerful rhetoric. But to what extent are we guilty of hypocrisy? Inspired by the title and theme of the conference ‘HRD: Reflecting upon the Past, Shaping the Future’ this paper seeks to make a critically reflective statement on our own practice as HRD academics teaching and researching reflective practice. Researching ‘practising what we preach’, in the context of reflective practice, raises difficult questions but offers the potential for valuable insight into the HRD academics’ professional practice

Carbon cycle dynamics during episodes of rapid climate change

Past climate records reveal many instances of rapid climate change that are often coincident with fast changes in atmospheric greenhouse gas concentrations, suggesting links and positive feedbacks between the carbon cycle and the physical climate system. The carbon reservoirs that might have played an important role during these past episodes of rapid change include near-surface soil and peatland carbon, permafrost, carbon stored in vegetation, methane hydrates in deep-sea sediments, volcanism, and carbon stored in parts of the ocean that are easily ventilated through changes in circulation. To determine whether similar changes might lie in store in our future, we must gain a better understanding of the physics, biogeochemistry, dynamics, and feedbacks involved in such events. Specifically, we need to ascertain the main natural sources of atmospheric carbon dioxide and methane linked to rapid climate events in the paleoclimate record, and understand the mechanisms, triggers, thresholds, and feedbacks that were involved. Our review contributes to this focus issue by synthesizing results from nine studies covering a broad range of past time episodes. Studies are categorized into (a) episodes of massive carbon release millions of years ago; (b) the transition from the last glacial to the current interglacial 19 000–11 000 years ago; and (c) the current era. We conclude with a discussion on major remaining research challenges and implications for future projections and risk assessment.Publisher PDFPeer reviewe

Constraining quasar host halo masses with the strength of nearby Lyman-alpha forest absorption

Using cosmological hydrodynamic simulations we measure the mean transmitted flux in the Lyman alpha forest for quasar sightlines that pass near a foreground quasar. We find that the trend of absorption with pixel-quasar separation distance can be fitted using a simple power law form including the usual correlation function parameters r_{0} and \gamma so that ( = \sum exp(-tau_eff*(1+(r/r_{0})^(-\gamma)))). From the simulations we find the relation between r_{0} and quasar mass and formulate this as a way to estimate quasar host dark matter halo masses, quantifying uncertainties due to cosmological and IGM parameters, and redshift errors. With this method, we examine data for ~3000 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 3, assuming that the effect of ionizing radiation from quasars (the so-called transverse proximity effect) is unimportant (no evidence for it is seen in the data.) We find that the best fit host halo mass for SDSS quasars with mean redshift z=3 and absolute G band magnitude -27.5 is log10(M/M_sun) = 12.48^{+0.53}_{-0.89}. We also use the Lyman-Break Galaxy (LBG) and Lyman alpha forest data of Adelberger et al in a similar fashion to constrain the halo mass of LBGs to be log10(M/M_sun) = 11.13^{+0.39}_{-0.55}, a factor of ~20 lower than the bright quasars. In addition, we study the redshift distortions of the Lyman alpha forest around quasars, using the simulations. We use the quadrupole to monopole ratio of the quasar-Lyman alpha forest correlation function as a measure of the squashing effect. We find that this does not have a measurable dependence on halo mass, but may be useful for constraining cosmic geometry.Comment: 10 pages, 11 figures, submitted to MNRA