Investigating the Rotational Phase of Stellar Flares on M dwarfs Using K2 Short Cadence Data

We present an analysis of K2 short cadence data of 34 M dwarfs which have spectral types in the range M0 - L1. Of these stars, 31 showed flares with a duration between $\sim$10-90 min. Using distances obtained from Gaia DR2 parallaxes, we determined the energy of the flares to be in the range $\sim1.2\times10^{29}-6\times10^{34}$ erg. In agreement with previous studies we find rapidly rotating stars tend to show more flares, with evidence for a decline in activity in stars with rotation periods longer than $\sim$10 days. The rotational modulation seen in M dwarf stars is widely considered to result from a starspot which rotates in and out of view. Flux minimum is therefore the rotation phase where we view the main starspot close to the stellar disk center. Surprisingly, having determined the rotational phase of each flare in our study we find none show any preference for rotational phase. We outline three scenarios which could account for this unexpected finding. The relationship between rotation phase and flare rate will be explored further using data from wide surveys such as NGTS and TESS.Comment: Accepted main Journal MNRA

When is electromagnetic spectrum fungible?

Fungibility is a common assumption for market-based spectrum management. In this paper, we explore the dimensions of practical fungibility of frequency bands from the point of view of the spectrum buyer who intends to use it. The exploration shows that fungibility is a complex, multidimensional concept that cannot casually be assumed. We develop two ideas for quantifying fungibility-(i) of a fungibility space in which the 'distance' between two slices of spectrum provides score of fungibility and (ii) a probabilistic score of fungibility. © 2012 IEEE

Attenuation of upstream-generated low frequency noise by gas turbines

The acoustic transfer functions of low frequency (below 3500 Hz) noise through aircraft turbines were investigated. Model test results were compared with theoretical predictions in order to assess the validity of the theory. Component tests were conducted on both high pressure and low pressure model turbines. The influence of inlet temperature and turbine speed attenuation was evaluated, while the effects of turbine pressure ratio, blade-row choking, and additional downstream stages were determined. Preliminary identification of pertinent aeroacoustic correlating parameters was made

Can coronal hole spicules reach coronal temperatures?

We aim with the present study to provide observational evidences on whether coronal hole spicules reach coronal temperatures. We combine multi-instrument co-observations obtained with the SUMER/SoHO and with the EIS/SOT/XRT/Hinode. The analysed three large spicules were found to be comprised of numerous thin spicules which rise, rotate and descend simultaneously forming a bush-like feature. Their rotation resembles the untwisting of a large flux rope. They show velocities ranging from 50 to 250 km/s. We clearly associated the red- and blue-shifted emissions in transition region lines with rotating but also with rising and descending plasmas, respectively. Our main result is that these spicules although very large and dynamic, show no presence in spectral lines formed at temperatures above 300 000 K. The present paper brings out the analysis of three Ca II H large spicules which are composed of numerous dynamic thin spicules but appear as macrospicules in EUV lower resolution images. We found no coronal counterpart of these and smaller spicules. We believe that the identification of phenomena which have very different origins as macrospicules is due to the interpretation of the transition region emission, and especially the He II emission, wherein both chromospheric large spicules and coronal X-ray jets are present. We suggest that the recent observation of spicules in the coronal AIA/SDO 171 A and 211 A channels is probably due to the existence of transition region emission there.Comment: 4 pages, 4 figures, accepted for publication in A&

A Stochastic Geometry Framework for LOS/NLOS Propagation in Dense Small Cell Networks

The need to carry out analytical studies of wireless systems often motivates the usage of simplified models which, despite their tractability, can easily lead to an overestimation of the achievable performance. In the case of dense small cells networks, the standard single slope path-loss model has been shown to provide interesting, but supposedly too optimistic, properties such as the invariance of the outage/coverage probability and of the spectral efficiency to the base station density. This paper seeks to explore the performance of dense small cells networks when a more accurate path-loss model is taken into account. We first propose a stochastic geometry based framework for small cell networks where the signal propagation accounts for both the Line-of-Sight (LOS) and Non-Line-Of-Sight (NLOS) components, such as the model provided by the 3GPP for evaluation of pico-cells in Heterogeneous Networks. We then study the performance of these networks and we show the dependency of some metrics such as the outage/coverage probability, the spectral efficiency and Area Spectral Efficiency (ASE) on the base station density and on the LOS likelihood of the propagation environment. Specifically, we show that, with LOS/NLOS propagation, dense networks still achieve large ASE gain but, at the same time, suffer from high outage probability.Comment: Typo corrected in eq. (3); Typo corrected in legend of Fig. 1-2; Typos corrected and definitions of some variables added in Section III.E; Final result unchanged; Paper accepted to IEEE ICC 201

A Characterization of all Solutions to the Four Block General Distance Problem

All solutions to the four block general distance problem which arises in H^∞ optimal control are characterized. The procedure is to embed the original problem in an all-pass matrix which is constructed. It is then shown that part of this all-pass matrix acts as a generator of all solutions. Special attention is given to the characterization of all optimal solutions by invoking a new descriptor characterization of all-pass transfer functions. As an application, necessary and sufficient conditions are found for the existence of an H^∞ optimal controller. Following that, a descriptor representation of all solutions is derived

Prevention of osteoporotic refractures in regional Australia

Objective: Clinical guidelines recommend that patients who sustain a minimal trauma fracture (MTF) should receive a bone mineral density (BMD) scan and bisphosphonate (or equivalent) therapy if diagnosed with osteoporosis. A pilot fracture liaison service (FLS) was implemented in regional NSW to improve adherence to the guidelines. Design: Prospective cohort study with an historical control. Setting: Primary care. Participants: Control (n = 47) and cohort (n = 93) groups comprised patients consenting to interview who presented with a MTF to the major referral hospital 4 months before and 12 months after FLS implementation respectively. Main outcome measures: Primary outcome measures were the rates of BMD scans and anti-osteoporotic medication initiation/review after MTF. Hospital admission data were also examined to determine death and refracture rates for all patients presenting during the study period with a primary diagnosis of MTF within 3 years of their initial fracture. Results: Although there was no improvement in BMD scanning rates, the reported rate of medication initiation/review after fracture was significantly higher (P \u3c 0.05) in the FLS cohort. However, once adjusted for age, this association was not significant (P = 0.086). There was a lower refracture rate during the cohort period (P = 0.013), however, there were significantly more deaths (P = 0.035) within 3 years of initial fracture. When deaths were taken into account via competing risk regression, patients in the cohort period were significantly less likely to refracture than those in the control period (Hazard ratio = 0.576, P = 0.032). Conclusions: A rurally based nurse-led FLS was associated with modest improvement after MTF. Consideration should be given to ways to strengthen the model of care to improve outcomes

The safety and sustainability of mining at diverse scales: Placing health and safety at the core of responsibility

Mining plays a major role in meeting global resource demands with Europe hosting extensive mineral potential. However, few of these prospects are feasible for conventional exploitation due to their small size & ore grade, proximity to dense populations and tenement constraints. Hence, a significant paradigm shift towards switch-on, switch off small-scale mining (SOSO SSM) is needed in order to increase the viability of small, complex, high-grade deposits. The IMP@CT project developed mobile, modularised solutions to facilitate rapid deployment and in-situ extraction & processing, which necessitates the translation and extension of best practice safety and sustainability from established national regulations and industry standards. Despite decades of accumulated safety regulation, knowledge and experience, workplace errors and violations still lead to fatal accidents, particularly if immature safety attitudes and behaviours pervade an organisation. The presence of a mature safety culture is vital for mitigating the occurrence of injuries and fatalities, through a collective commitment to safety improvement. This study has aimed to consolidate safety and sustainability best practice that is tailored to SSM by identifying the critical safety considerations and applying safety culture maturity principles to the specific challenges associated with a semi-automated SOSO SSM system. Criteria-driven maturity modelling, informed by existing responsible mining initiatives and safety and socio-environmental culture perspectives from site personnel at all hierarchical levels, is developed to assess the environmental and social factors associated with small- to medium-scale regulated mining. The role of agile management for rapid adaptation and continuous improvement of safety and sustainability performance in SOSO SSM is discussed. This research has demonstrated that for SOSO SSM to effectively integrate a mature safety and socio-environmental culture within a flexible, containerised mining paradigm, managerial and technical agility, and human initiative must be encouraged to continuously drive progress in occupational health and safety and generate wider societal benefit

The U.S. Navy and War Plan Orange, 1933-1940: Making Necessity a Virtue

In October 1940 Capt. A.W. Clarke, R,N,, the British Government\u27s personal liaison with President Franklin Roosevelt, received an invitation ro visit the Navy Department\u27s War Plans Division. Once there, Clarke\u27s host, Capt. Richmond Kelley Turner, ushered him into a room, unlocked a safe, and presented him with a document that proved to be the U.S. Navy\u27s operational plans for war with Japan Left alone and encouraged to read, the British captain was astonished at the amount of detail the plans contained