29 research outputs found
Interface Management for SKA Telescope Manager
The Square Kilometre Array (SKA) project is currently in the Pre-construction Phase. During this phase, the telescope subsystems are being designed. The Telescope Manager (TM) is a supervisory control and monitoring subsystem in each of the two radio telescopes of the SKA (SKA1-Low and SKA1-Mid). The TM interfaces with a number of diverse telescope subsystems. Interaction between TM and these subsystems is a major source of requirements for the TM. Careful management of TM external interfaces is therefore important. This discussion is a case study of TM interface management. Firstly, how system architectural design aspects like separation of concerns in the control hierarchy reduce telescope complexity with regards to interfaces is discussed. Secondly, the standardisation approach for monitoring and control interfaces to facilitate early elicitation of interface requirements for the TM, and to manage the diversity of interfacing subsystems is discussed. Thirdly, the relations between interface definition and requirements analysis activities, using SysML representations as an example is discussed
Testing Target Independence of the `Proton Spin' Effect in Semi-Inclusive Deep Inelastic Scattering
A natural consequence of the composite operator propagator-vertex description
of deep inelastic scattering developed by the authors is that the anomalous
suppression observed in the flavour singlet contribution to the first moment of
the polarised proton structure function (the `proton spin' problem) is
not a special property of the proton structure but is a target independent
effect which can be related to an anomalous suppression in the QCD topological
susceptibility. In this paper, it is shown how this target independent
mechanism can be tested in semi-inclusive deep inelastic scattering in which a
pion or D meson carrying a large target energy fraction is detected in the
target fragmentation region.Comment: 23 pages, TeX, includes 11 ps figure
A Test of Target Independence of the `Proton Spin' Effect in Semi-Inclusive Deep Inelastic Scattering
The target-independent suppression mechanism proposed as an explanation of
the EMC-SMC `proton spin' effect is reviewed and compared to current
experimental data. According to this proposal, the anomalous suppression
observed in the first moment of the polarised proton structure function g_1^p
is not a special property of the proton structure, but reflects an anomalously
small value of the first moment of the QCD topological susceptibility. It is
shown how this mechanism can be tested in semi-inclusive DIS processes in which
a pion or D meson carrying a large target energy fraction z is detected in the
target fragmentation region
Developing a predictive modelling capacity for a climate change-vulnerable blanket bog habitat: Assessing 1961-1990 baseline relationships
Aim: Understanding the spatial distribution of high priority habitats and
developing predictive models using climate and environmental variables to
replicate these distributions are desirable conservation goals. The aim of this
study was to model and elucidate the contributions of climate and topography to
the distribution of a priority blanket bog habitat in Ireland, and to examine how
this might inform the development of a climate change predictive capacity for
peat-lands in Ireland.
Methods: Ten climatic and two topographic variables were recorded for grid
cells with a spatial resolution of 1010 km, covering 87% of the mainland
land surface of Ireland. Presence-absence data were matched to these variables
and generalised linear models (GLMs) fitted to identify the main climatic and
terrain predictor variables for occurrence of the habitat. Candidate predictor
variables were screened for collinearity, and the accuracy of the final fitted GLM
was evaluated using fourfold cross-validation based on the area under the curve
(AUC) derived from a receiver operating characteristic (ROC) plot. The GLM
predicted habitat occurrence probability maps were mapped against the actual
distributions using GIS techniques.
Results: Despite the apparent parsimony of the initial GLM using only climatic
variables, further testing indicated collinearity among temperature and precipitation
variables for example. Subsequent elimination of the collinear variables and
inclusion of elevation data produced an excellent performance based on the AUC
scores of the final GLM. Mean annual temperature and total mean annual
precipitation in combination with elevation range were the most powerful
explanatory variable group among those explored for the presence of blanket
bog habitat.
Main conclusions: The results confirm that this habitat distribution in general
can be modelled well using the non-collinear climatic and terrain variables tested
at the grid resolution used. Mapping the GLM-predicted distribution to the
observed distribution produced useful results in replicating the projected
occurrence of the habitat distribution over an extensive area. The methods
developed will usefully inform future climate change predictive modelling for
Irelan
State of the climate in 2018
In 2018, the dominant greenhouse gases released into Earth’s atmosphere—carbon dioxide, methane, and nitrous oxide—continued their increase. The annual global average carbon dioxide concentration at Earth’s surface was 407.4 ± 0.1 ppm, the highest in the modern instrumental record and in ice core records dating back 800 000 years. Combined, greenhouse gases and several halogenated gases contribute just over 3 W m−2 to radiative forcing and represent a nearly 43% increase since 1990. Carbon dioxide is responsible for about 65% of this radiative forcing. With a weak La Niña in early 2018 transitioning to a weak El Niño by the year’s end, the global surface (land and ocean) temperature was the fourth highest on record, with only 2015 through 2017 being warmer. Several European countries reported record high annual temperatures. There were also more high, and fewer low, temperature extremes than in nearly all of the 68-year extremes record. Madagascar recorded a record daily temperature of 40.5°C in Morondava in March, while South Korea set its record high of 41.0°C in August in Hongcheon. Nawabshah, Pakistan, recorded its highest temperature of 50.2°C, which may be a new daily world record for April. Globally, the annual lower troposphere temperature was third to seventh highest, depending on the dataset analyzed. The lower stratospheric temperature was approximately fifth lowest. The 2018 Arctic land surface temperature was 1.2°C above the 1981–2010 average, tying for third highest in the 118-year record, following 2016 and 2017. June’s Arctic snow cover extent was almost half of what it was 35 years ago. Across Greenland, however, regional summer temperatures were generally below or near average. Additionally, a satellite survey of 47 glaciers in Greenland indicated a net increase in area for the first time since records began in 1999. Increasing permafrost temperatures were reported at most observation sites in the Arctic, with the overall increase of 0.1°–0.2°C between 2017 and 2018 being comparable to the highest rate of warming ever observed in the region. On 17 March, Arctic sea ice extent marked the second smallest annual maximum in the 38-year record, larger than only 2017. The minimum extent in 2018 was reached on 19 September and again on 23 September, tying 2008 and 2010 for the sixth lowest extent on record. The 23 September date tied 1997 as the latest sea ice minimum date on record. First-year ice now dominates the ice cover, comprising 77% of the March 2018 ice pack compared to 55% during the 1980s. Because thinner, younger ice is more vulnerable to melting out in summer, this shift in sea ice age has contributed to the decreasing trend in minimum ice extent. Regionally, Bering Sea ice extent was at record lows for almost the entire 2017/18 ice season. For the Antarctic continent as a whole, 2018 was warmer than average. On the highest points of the Antarctic Plateau, the automatic weather station Relay (74°S) broke or tied six monthly temperature records throughout the year, with August breaking its record by nearly 8°C. However, cool conditions in the western Bellingshausen Sea and Amundsen Sea sector contributed to a low melt season overall for 2017/18. High SSTs contributed to low summer sea ice extent in the Ross and Weddell Seas in 2018, underpinning the second lowest Antarctic summer minimum sea ice extent on record. Despite conducive conditions for its formation, the ozone hole at its maximum extent in September was near the 2000–18 mean, likely due to an ongoing slow decline in stratospheric chlorine monoxide concentration. Across the oceans, globally averaged SST decreased slightly since the record El Niño year of 2016 but was still far above the climatological mean. On average, SST is increasing at a rate of 0.10° ± 0.01°C decade−1 since 1950. The warming appeared largest in the tropical Indian Ocean and smallest in the North Pacific. The deeper ocean continues to warm year after year. For the seventh consecutive year, global annual mean sea level became the highest in the 26-year record, rising to 81 mm above the 1993 average. As anticipated in a warming climate, the hydrological cycle over the ocean is accelerating: dry regions are becoming drier and wet regions rainier. Closer to the equator, 95 named tropical storms were observed during 2018, well above the 1981–2010 average of 82. Eleven tropical cyclones reached Saffir–Simpson scale Category 5 intensity. North Atlantic Major Hurricane Michael’s landfall intensity of 140 kt was the fourth strongest for any continental U.S. hurricane landfall in the 168-year record. Michael caused more than 30 fatalities and 6 billion (U.S. dollars) in damages across the Philippines, Hong Kong, Macau, mainland China, Guam, and the Northern Mariana Islands. Tropical Storm Son-Tinh was responsible for 170 fatalities in Vietnam and Laos. Nearly all the islands of Micronesia experienced at least moderate impacts from various tropical cyclones. Across land, many areas around the globe received copious precipitation, notable at different time scales. Rodrigues and Réunion Island near southern Africa each reported their third wettest year on record. In Hawaii, 1262 mm precipitation at Waipā Gardens (Kauai) on 14–15 April set a new U.S. record for 24-h precipitation. In Brazil, the city of Belo Horizonte received nearly 75 mm of rain in just 20 minutes, nearly half its monthly average. Globally, fire activity during 2018 was the lowest since the start of the record in 1997, with a combined burned area of about 500 million hectares. This reinforced the long-term downward trend in fire emissions driven by changes in land use in frequently burning savannas. However, wildfires burned 3.5 million hectares across the United States, well above the 2000–10 average of 2.7 million hectares. Combined, U.S. wildfire damages for the 2017 and 2018 wildfire seasons exceeded $40 billion (U.S. dollars)
Recommended from our members
Rapid growth rates of syndepositional marine aragonite cements in steep marginal slope deposits, Bahamas and Belize
Growth rates of marine botryoidal aragonite cements from steep (35-45[degree]) marginal slope deposits in the Bahamas and Belize have been determined by accelerator mass spectrometer radiocarbon dating of samples taken at the base and top of individual botryoids. The pore-filling cements, which range from approximately 11,000-13,000 years old, grew at average rates of 8-10mm/100 yr with maximum rates > 25mm/100 yr. Radiocarbon dating of coexisting skeletal components indicates that cementation was syndepositional. Microsampling transects across individual botryoids for stable-isotope analyses show little variation in [delta][sup 31]C and [delta][sup 18]O, supporting the conclusion that cementation was extremely rapid. Although the cements show a progressive depletion in isotopic composition of approximately 1[per thousand]([delta][sup 13]C) and 2[per thousand]([delta][sup 18]O) from 13 ka to 11 ka, the average variation ([delta][sub 1]) within individual pore-filling cements, ranging in size 2 mm to 32 mm (bottom to top), was 0.11[per thousand]([delta][sup 13]C) and 0.14[per thousand]([delta][sup 18]O). Results of this study provide the first quantitative data on growth rates of marine carbonate cements in a marginal slope environment. The data indicate that marginal slope deposits may lithify within several tens of years and suggest that geologically instantaneous cementation may be critical in stabilizing steep carbonate slope deposits at or above angles of repose