scholarly journals On the Relationship between Low Latitude Scintillation Onset and Sunset Terminator over Africa

2021 ◽  
Vol 13 (11) ◽  
pp. 2087
Author(s):  
Mogese Wassaie Mersha ◽  
Elias Lewi ◽  
Norbert Jakowski ◽  
Volker Wilken ◽  
Jens Berdermann ◽  
...  
Keyword(s):  
Moving Boundary ◽  
Occurrence Rate ◽  
Scintillation Index ◽  
Small Scale ◽  
Bahir Dar ◽  
Remarkable Change ◽  
Equatorial Africa ◽  
Night Side ◽  
Solar Terminator ◽  
First Time

The solar terminator is a moving boundary between day-side and night-side regions on the Earth, which is a substantial source of perturbations in the ionosphere. In the vicinity of the solar terminator, essential parameters like S4 index measurements are widely analyzed in order to monitor and predict perturbations in the ionosphere. The utilization of the scintillation index S4 is a well-accepted approach to describe the amplitude/intensity fluctuation of a received signal, predominantly caused by small-scale irregularities of the ionospheric plasma. We report on the longitudinal daily and seasonal occurrence of GNSS signal scintillations, using the data derived from the GNSS stations in Bahir Dar, Ethiopia, Lomé, Togo and Dakar, Senegal. The observed seasonal climatology of GNSS signal scintillations in equatorial Africa is adequately explained by the alignment of the solar terminator and local geomagnetic declination line. It should be pointed out that the strongest scintillations are most frequently observed during the time when the solar terminator is best aligned with the geomagnetic declination line. At all three stations, the comparison of computational and observational results indicated that the scintillation activity culminated around equinoxes in the years 2014, 2015 and 2016. Comparatively, the western equatorial Africa sector has the most intense, longest-lasting, and highest scintillation occurrence rate in equinoctial seasons in all three years. For the first time, we show that the seasonal variation of the scintillation peaks changes systematically from west to east at equatorial GNSS stations over Africa. A detailed analysis of the solar day–night terminator azimuth at ionospheric heights including the time equation shows that the scintillation intensity has a maximum if the azimuth of the terminator coincides with the declination line of the geomagnetic field. Due to the remarkable change of the declination by about 10° at the considered GNSS stations, the distance between scintillation peaks increases by 46 days when moving westward from the Bahir Dar to the Dakar GNSS station. The observations agree quite well with the computational results, thus confirming Tsunoda’s theory.

Corrosion Testing of Armour Wire in Simulated Annulus Environments of Flexible Pipelines: An Update

2003 ◽  
Author(s):  
Richard Clements ◽  
Andrew D. Ethridge
Keyword(s):  
Deionized Water ◽  
Small Scale ◽  
General Corrosion ◽  
Flexible Pipe ◽  
Scale Test ◽  
Condensed Water ◽  
Test Cells ◽  
Sour Service ◽  
First Time ◽  
Permeation Models

This paper describes further investigations, utilising small scale test cells, into the general corrosion which can occur on wires within the inherent annulus space in a flexible pipe, particularly, and for the first time, in a sour service (H2S containing) environment. The work enhances data presented previously in 2002. Tests have been performed in cells specifically designed to simulate, as closely as possible, the environment and confines of a flexible pipe annulus, using solutions of both deionized water and seawater (to represent seawater flooding and condensed water). The systems were saturated with CO2 and H2S to simulate permeation of gases through the polymer pressure sheath (as predicted by validated permeation models). Weight loss measurements were undertaken in order to quantify the corrosion rate in these simulated annulus environments and metallography was undertaken to characterise the corrosion and check for HIC/SOHIC.

scholarly journals “Audience exchange”: cultivating peer-to-peer dialogue at unfamiliar arts events

2017 ◽  
Vol 7 (1) ◽  
pp. 65-79 ◽  
Author(s):  
Stephanie Pitts ◽  
Jonathan Gross
Keyword(s):  
Peer Learning ◽  
Peer To Peer ◽  
Small Scale ◽  
Exchange Method ◽  
Audience Engagement ◽  
Content Type ◽  
Peer Dialogue ◽  
Targeted Marketing ◽  
Audience Development ◽  
First Time

Purpose The purpose of this paper is to demonstrate the usefulness of the “audience exchange” approach for audience development and research, and to highlight the insights offered by peer-to-peer dialogue in understanding experiences of unfamiliar arts. Design/methodology/approach Using a case study with contemporary arts audiences, and setting this in the wider context of studies with other first-time attenders at a range of arts events, the paper explores the use of the “audience exchange” method, in which facilitated conversations after performance events allow newcomers to reflect upon and deepen their first-time encounters with live arts. Findings The study demonstrates the way in which conversations about arts events can enrich audience experience, and shows how participants use exploratory and emotional language to articulate their understanding of unfamiliar arts events. Peer-to-peer learning occurs through these conversations, in ways that could be further supported by arts organisations as a valuable tool for audience development. The audience exchange discussions also reveal the varieties of participation from “drifting” to full attention that are all part of audience engagement. Research limitations/implications This is a small-scale, qualitative study, and the method has potential to be tested in future studies with a greater variety of participants (e.g. younger or more ethnically diverse groups). Practical implications Use of the audience exchange for enriching experiences of first-time attendance could be adopted by arts organisations as a regular part of their audience engagement. Greater understanding of how new audience members draw on prior cultural experiences in finding the language to articulate their first impressions of an unfamiliar arts event could be valuable for targeted marketing and increasing accessibility. Originality/value The originality of this study lies in its elaboration of the audience exchange method, and its focus on the language and peer-to-peer learning evident in the facilitated post-performance discussions.

scholarly journals Transient brightenings in the quiet Sun detected by ALMA at 3 mm

2020 ◽  
Vol 638 ◽  
pp. A62 ◽  
Author(s):  
A. Nindos ◽  
C. E. Alissandrakis ◽  
S. Patsourakos ◽  
T. S. Bastian
Keyword(s):  
Solar Atmosphere ◽  
Power Law ◽  
Small Scale ◽  
Solar Chromosphere ◽  
Average Intensity ◽  
Quiet Sun ◽  
Brightness Temperatures ◽  
Weak Preference ◽  
Thermal Origin ◽  
First Time

Aims. We investigate transient brightenings, that is, weak, small-scale episodes of energy release, in the quiet solar chromosphere; these episodes can provide insights into the heating mechanism of the outer layers of the solar atmosphere. Methods. Using Atacama Large Millimeter/submillimeter Array (ALMA) observations, we performed the first systematic survey for quiet Sun transient brightenings at 3 mm. Our dataset included images of six 87″ × 87″ fields of view of the quiet Sun obtained with angular resolution of a few arcsec at a cadence of 2 s. The transient brightenings were detected as weak enhancements above the average intensity after we removed the effect of the p-mode oscillations. A similar analysis, over the same fields of view, was performed for simultaneous 304 and 1600 Å data obtained with the Atmospheric Imaging Assembly. Results. We detected 184 3 mm transient brightening events with brightness temperatures from 70 K to more than 500 K above backgrounds of ∼7200 − 7450 K. All events showed light curves with a gradual rise and fall, strongly suggesting a thermal origin. Their mean duration and maximum area were 51.1 s and 12.3 Mm2, respectively, with a weak preference of appearing at network boundaries rather than in cell interiors. Both parameters exhibited power-law behavior with indices of 2.35 and 2.71, respectively. Only a small fraction of ALMA events had either 304 or 1600 Å counterparts but the properties of these events were not significantly different from those of the general population except that they lacked their low-end energy values. The total thermal energies of the ALMA transient brightenings were between 1.5 × 1024 and 9.9 × 1025 erg and their frequency distribution versus energy was a power law with an index of 1.67 ± 0.05. We found that the power per unit area provided by the ALMA events could account for only 1% of the chromospheric radiative losses (10% of the coronal ones). Conclusions. We were able to detect, for the first time, a significant number of weak 3 mm quiet Sun transient brightenings. However, their energy budget falls short of meeting the requirements for the heating of the upper layers of the solar atmosphere and this conclusion does not change even if we use the least restrictive criteria possible for the detection of transient brightenings.

scholarly journals THE ADAPTED YAM MINISETT TECHNIQUE FOR PRODUCING CLEAN SEED YAMS (DIOSCOREA ROTUNDATA): AGRONOMIC PERFORMANCE AND VARIETAL DIFFERENCES UNDER FARMER-MANAGED CONDITIONS IN NIGERIA

2014 ◽  
Vol 51 (3) ◽  
pp. 467-482 ◽  
Author(s):  
STEPHEN MORSE ◽  
NORA McNAMARA
Keyword(s):  
Small Scale ◽  
Agronomic Performance ◽  
Economic Returns ◽  
Dioscorea Rotundata ◽  
Pesticide Treatment ◽  
Planting Material ◽  
Clean Seed ◽  
Small Scale Farmers ◽  
Major Factors ◽  
First Time

SUMMARYWhite yam (Dioscorea rotundata) is a major root crop grown throughout West Africa but one of the major factors that limits its production is the availability of good quality planting material. This paper described the results of farmer-managed demonstration plots established in 2012 and 2013 designed to promote the Adapted Yam Minisett Technique (AYMT) in Nigeria. The AYMT was developed between 2005 and 2008 to produce quality seed yam tubers at a cost that is viable for small-scale farmers. Since its development the agronomic performance of AYMT has not been explored across a large sample of farmers, and neither has there been any attempt to explore possible varietal effects although farmers have often alluded to this. This papers seeks to address these gaps in the literature and the results suggest that the AYMT does succeed in producing seed yams of the required size and the economic returns are also good. Results also suggest that there is a varietal affect with AYMT, including a significant interaction with pesticide treatment; the first time this has been demonstrated.

scholarly journals Wobbly discs – corrugations seen in the dust lanes of edge-on galaxies

2020 ◽  
Vol 495 (4) ◽  
pp. 3705-3714
Author(s):  
Chaitra A Narayan ◽  
Ralf-Jürgen Dettmar ◽  
Kanak Saha
Keyword(s):  
Stability Analysis ◽  
Small Scale ◽  
Host Galaxies ◽  
Lower Mass ◽  
Limited Sample ◽  
Unsharp Masking ◽  
Bending Waves ◽  
First Time ◽  
Larger Sample ◽  
Disc Galaxies

ABSTRACT We report the detection of small-scale bending waves, also known as corrugations, in the dust lanes of five nearby edge-on disc galaxies. This phenomenon, where the disc mid-plane bends to become wavy, just as in warps but on a smaller scale, is seen here for the first time, in the dust lanes running across the discs. Because they are seen in absorption, this feature must be present in the dust disc in the outskirts of these galaxies. We enhance the visibility of these features using unsharp masking, trace the dust mid-plane across the disc, measure the corrugation amplitude by eye and the corrugation wavelength using Fourier analysis. The corrugation amplitude is found to be in the range of 70–300pc and the wavelengths lie between 1 and 5 kpc. In this limited sample, we find that the amplitude of the corrugations tends to be larger for lower mass galaxies, whereas the wavelength of corrugation does not seem to depend on the mass of host galaxies. Linear stability analysis is performed to find out the dynamical state of these dust discs. Based on WKB analysis, we find that the dust corrugations in about half of our sample are stable. Further analysis, on a larger sample would be useful to strengthen the above results.

scholarly journals Optimisation of confinement in a fusion reactor using a nonlinear turbulence model

2018 ◽  
Vol 84 (2) ◽  
Author(s):  
E. G. Highcock ◽  
N. R. Mandell ◽  
M. Barnes ◽  
W. Dorland
Keyword(s):  
First Principles ◽  
Figure Of Merit ◽  
Large Scale ◽  
Unit Volume ◽  
Fusion Reactor ◽  
Small Scale ◽  
Zonal Flows ◽  
Novel Approach ◽  
First Time ◽  
Turbulent Cascade

The confinement of heat in the core of a magnetic fusion reactor is optimised using a multidimensional optimisation algorithm. For the first time in such a study, the loss of heat due to turbulence is modelled at every stage using first-principles nonlinear simulations which accurately capture the turbulent cascade and large-scale zonal flows. The simulations utilise a novel approach, with gyrofluid treatment of the small-scale drift waves and gyrokinetic treatment of the large-scale zonal flows. A simple near-circular equilibrium with standard parameters is chosen as the initial condition. The figure of merit, fusion power per unit volume, is calculated, and then two control parameters, the elongation and triangularity of the outer flux surface, are varied, with the algorithm seeking to optimise the chosen figure of merit. A twofold increase in the plasma power per unit volume is achieved by moving to higher elongation and strongly negative triangularity.

scholarly journals Solar activities observed with the New Vacuum Solar Telescope

2015 ◽  
Vol 11 (S320) ◽  
pp. 315-320
Author(s):  
Shuhong Yang ◽  
Jun Zhang
Keyword(s):  
Magnetic Reconnection ◽  
Flux Rope ◽  
Observational Evidence ◽  
Small Scale ◽  
Solar Telescope ◽  
New Name ◽  
Direct Observations ◽  
Filament Activation ◽  
First Time

AbstractBased on the New Vacuum Solar Telescope observations, some new results about the solar activities are obtained. (1) In the Hα line, a flux rope tracked by filament activation is detected for the first time. There may exist some mild heating during the filament activation. (2) The direct observations illustrate the mechanism of confined flares, i.e., the flares are triggered by magnetic reconnection between the emerging loops and the pre-existing loops and prevented from being eruptive by the overlying loops. (3) The solid observational evidence of magnetic reconnection between two sets of small-scale loops is reported. The successive slow reconnection changes the conditions around the reconnection area and leads to the rapid reconnection. (4) An ensemble of oscillating bright features rooted in a light bridge is observed and given a new name, light wall. The light wall oscillations may be due to the leakage of p-modes from below the photosphere.

Flow Visualization Study of Jet and Bucket Interactions in Traditional and Hooped Pelton Runner

2019 ◽  
Author(s):  
Gaurangkumar Chaudhari ◽  
Salim Channiwala ◽  
Samip Shah ◽  
Digvijay Kulshreshtha
Keyword(s):  
Flow Visualization ◽  
Flow Pattern ◽  
High Speed ◽  
Early Stage ◽  
Small Scale ◽  
High Speed Photography ◽  
Pelton Turbine ◽  
Single Jet ◽  
Absolute Frame ◽  
First Time

Abstract This paper aims to study the flow pattern in and around a bucket of a Traditional and a Hooped Pelton runner at single injector operation and illustrates different stages of jet interaction. High speed photography is used to study the flow pattern, keeping the camera in different positions relative to the jet and to the bucket. It is concluded from the results that the flow visualization study, provides exceptional observations with an absolute frame of reference to mark the bucket duty period of a single-jet Pelton runner. The small scale models display erosion damages at the bucket lips, this indicated that the high pressure occur in the early stage of interaction. This fact is substantiated by the present flow visualization studies for the first time. The uncertainty of the free surface outflow within the Pelton turbine bucket establishes good documentation. The results are helpful to know the interaction between the jet and bucket of Pelton turbine.

scholarly journals Morphological diversity of the stone crayfish − traditional and geometric morphometric approach

2019 ◽  
pp. 1 ◽  
Author(s):  
Leona Lovrenčić ◽  
Vjera Pavić ◽  
Stefan Majnarić ◽  
Lucija Abramović ◽  
Mišel Jelić ◽  
...  
Keyword(s):  
Morphological Variability ◽  
Morphological Characteristics ◽  
Morphological Diversity ◽  
Dorsal Side ◽  
Small Scale ◽  
Geometric Morphometric ◽  
Discriminant Analyses ◽  
Stone Crayfish ◽  
Multivariate Discriminant ◽  
First Time

Austropotamobius torrentium is one of four native European crayfish species inhabiting Croatian freshwaters. Existence of eight divergent monophyletic mtDNA phylogroups was described within A. torrentium; six of them are distributed in Croatia, with the highest genetic diversity established in its northern-central Dinaric region. Recent small-scale study of the stone crayfish morphological variability indicated significant differences among different phylogroups. In the present study larger sample size, covering populations from five phylogroups, was analysed with the aim of determining whether there are morphological characteristics that reliably separate stone crayfish from different phylogroups. Aiming this, 245 stone crayfish were analysed through traditional (TM) and, for the first time, geometric morphometric (GM) analyses. Multivariate discriminant analyses included 24 TM characteristics per crayfish, while GM comprised analyses of 22 landmarks on the dorsal side of cephalon. Both methods revealed congruent results, and significant differences among phylogroups in analysed features were obtained, with the cephalon shape contributing the most to crayfish discrimination. Research confirmed that both approaches, combined with statistical methods, are useful in distinguishing and separating crayfish phylogroups. Findings of present study are compatible with the previous molecular findings; stone crayfish present several distinct evolutionary lineages whose species status are currently undefined and require urgent clarification.

scholarly journals Future-proofing placements

2019 ◽  
Vol 9 (3) ◽  
pp. 434-444
Author(s):  
Julie Fowlie ◽  
Clare Forder
Keyword(s):  
Business School ◽  
Detailed Examination ◽  
Local Context ◽  
Small Scale ◽  
Local Economies ◽  
Content Type ◽  
Student Demand ◽  
First Time ◽  
Practical Implications

Purpose The purpose of this paper is to present a case study centred on steps taken at a Business School in a UK university, to improve local work placement provision, respond to student demand and engage more productively with local businesses. It is situated against renewed focus on universities’ engagement with local economies and the graduate labour market context as demonstrated by the government’s Industrial Strategy (BEIS, 2017) and the OfS (2018) business plan. It aims to emphasise how moving the focus back from graduates to placement students could offer a useful collaborative opportunity for local businesses to articulate what they want from future employees. Design/methodology/approach The paper follows a mixed methods approach, drawing upon a case study on a new intervention piloted in the Business School as well as qualitative research gathered from questionnaires and interviews with students. Responses to questionnaires and interviews were analysed thematically in the Grounded Theory (Glaser and Strauss, 1967) tradition. Findings The paper highlights the lack of literature on local placements and also demonstrates findings which echo existing research on typical barriers and drivers to placements in general. It offers original outcomes such as how for some students local placements offer a convenience value but for others they are part of committing to living and working locally after graduation. Research limitations/implications The small-scale nature of the study means that only indicative findings are presented. Further research is necessary for a more detailed examination of its implications. Practical implications Recommendations are made for a systematic approach to developing, or establishing for the first time, university–employer relationships in order to future-proof local placement opportunities. Originality/value The paper fills a gap in the literature on local placements and also provides a fresh approach to how universities and employers might work together to identify local skills gaps and increase the provision of local placements. It also offers ways in students’ often negatively framed reasons for not undertaking a placement can be mitigated through engaging with the local context.

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