Joint space-time trellis decoding and channel estimation in correlated fading channels

This letter addresses the issue of joint space-time trellis decoding and channel estimation in time-varying fading channels that are spatially and temporally correlated. A recursive space-time receiver which incorporates per-survivor processing (PSP) and Kalman filtering into the Viterbi algorithm is proposed. This approach generalizes existing work to the correlated fading channel case. The channel time-evolution is modeled by a multichannel autoregressive process, and a bank of Kalman filters is used to track the channel variations. Computer simulation results show that a performance close to the maximum likelihood receiver with perfect channel state information (CSI) can be obtained. The effects of the spatial correlation on the performance of a receiver that assumes independent fading channels are examined.

Antenna selection and channel estimation for hybrid relay systems

The research addressed performance issues for wireless signal transmission and has shown that performance improves with the help of relays due to increased diversity. Further, the areas of antenna selection and channel estimation and modelling has been investigated for improved cost and complexity and has shown to further enhance the performance of the wireless relay systems.

Long-term changes in abundance and distribution of microzooplankton in the NE Atlantic and North Sea

Long-term changes in mesozooplankton and phytoplankton populations have been well documented in the North Atlantic region, whereas data for microzooplankton are scarce. This neglected component of the plankton is a vital link in marine food-webs, grazing on smaller flagellates and cyanobacteria and in turn providing food for the larger mesozooplankton. We use the latest tintinnid (Ciliophora, Protista) data from the Continuous Plankton Recorder (CPR) survey in the NE Atlantic and North Sea to examine the phenology, distribution and abundance of this important group of ciliates. Presence/absence data came from 167 122 CPR samples collected between 1960 and 2009 and abundance data from 49 662 samples collected between 1996 and 2009. In the North Atlantic the genus Dictyocysta spp. dominated and Parafavella gigantea showed an increase in abundance around Iceland and Greenland. In the North Sea higher densities of Tintinnopsis spp., Favella serrata and Ptychocylis spp. were found. The presence of tintinnids in CPR samples collected in the North Atlantic has increased over the last 50 years and the seasonal window of high abundance has lengthened. Conversely in the North Sea there has been an overall reduction in abundance. We discuss possible drivers for these long-term changes and point the way forward to more holistic studies that examine how ecosystems, rather than just selected taxa, are responding to climate change.

Influence of deformation conditions and texture on the high temperature flow stress of magnesium AZ31

The evolution of hot working flow stress with strain is examined in torsion, uniaxial compression and channel die compression. The flow stress was found to be strongly dependent on texture and deformation mode. At low strains this dependency accounted for a difference in flow stress of up to a factor of two. At higher strains the influence of texture and deformation mode was less marked. The stresses corresponding to an equivalent strain of 0.5 were modelled using a power law expression with an activation energy of 147 kJ/mol and a strain rate exponent of 0.15. The influence of texture and deformation mode on flow stress is rationalised in terms of the influence of prismatic slip, twinning and dynamic recrystallisation on deformation stress and structure.

Palaeobiogeographic significance of Jurassic and Cretaceous Western Australian ostracod faunas

The palaeobiogeographic distribution of Western Australian ostracods during the Jurassic and Cretaceous illustrates how Gondwana broke apart to form the South Atlantic and Indian Oceans, and how the new ostracod genera from here migrated into the Atlantic Ocean, Mediterranean Sea, Western Pacific Ocean and the Western Indian Ocean.

Ontogenetic and seasonal variation in the Diel Vertical Migration of the Copepods Metridia lucens and Metridia longa

Plankton samples collected and analyzed by the Continuous Plankton Recorder survey were used to examine the length of time spent near the surface in the North Atlantic and the North Sea by three closely related groups of zooplankton (copepodite stages 1-4 Metridia spp., copepodite stages 5-6 Metridia lucens, and copepodite stages 5-6 Metridia longa). For all three groups, the mean daily length of time spent near the surface in each month of the year covaried seasonally with day length. In addition, the amount of time spent near the surface varied significantly between the three groups, being longest for the copepods of smallest body size (C 1-C4 Metridia spp.) and shortest for the copepods of largest body size (C5-C6 M. longa). These results support the suggestion that diel vertical migration serves to reduce the risk of mortality from visually orienting predators

Coccolithophores and the Continuous Plankton Recorder Survey

Samples historically collected and analysed by the Continuous Plankton Recorder (CPR) survey were used to describe the distribution of coccolithophores (class Prymnesiophyceae) in the north-east Atlantic and the North Sea. In the routine CPR analysis, members of this group are simply identified as ‘coccolithophores’ and not to any further taxonomic level. From this analysis, the 200-m depth contour marked a point of distinct transition between high coccolithophore occurrence (off the shelf) and low coccolithophore occurrence (on the shelf). Thirty-three CPR samples that had been collected between 1979–1992, were re-examined and the coccolithophores identified to a more detailed taxonomic level. Among the species identified was the bloom-forming coccolithophore, Emiliania huxleyi. Thus archived CPR samples could potentially be re-analysed to assess regional, seasonal and decadal changes in the occurrence of this species.

Changes in marine dinoflagellate and diatom abundance under climate change

Marine diatoms and dinoflagellates play a variety of key ecosystem roles as important primary producers (diatoms and some dinoflagellates) and grazers (some dinoflagellates). Additionally some are harmful algal bloom (HAB) species and there is widespread concern that HAB species may be increasing accompanied by major negative socio-economic impacts, including threats to human health and marine harvesting1, 2. Using 92,263 samples from the Continuous Plankton Recorder survey, we generated a 50-year (1960–2009) time series of diatom and dinoflagellate occurrence in the northeast Atlantic and North Sea. Dinoflagellates, including both HAB taxa (for example, Prorocentrum spp.) and non-HAB taxa (for example, Ceratium furca), have declined in abundance, particularly since 2006. In contrast, diatom abundance has not shown this decline with some common diatoms, including both HAB (for example, Pseudo-nitzschia spp.) and non-HAB (for example, Thalassiosira spp.) taxa, increasing in abundance. Overall these changes have led to a marked increase in the relative abundance of diatoms versus dinoflagellates. Our analyses, including Granger tests to identify criteria of causality, indicate that this switch is driven by an interaction effect of both increasing sea surface temperatures combined with increasingly windy conditions in summer.

Pan-atlantic analysis of the overlap of a highly migratory species, the leatherback turtle, with pelagic longline fisheries

Large oceanic migrants play important roles in ecosystems, yet many species are of conservation concern as a result of anthropogenic threats, of which incidental capture by fisheries is frequently identified. The last large populations of the leatherback turtle, Dermochelys coriacea, occur in the Atlantic Ocean, but interactions with industrial fisheries could jeopardize recent positive population trends, making bycatch mitigation a priority. Here, we perform the first pan-Atlantic analysis of spatio-temporal distribution of the leatherback turtle and ascertain overlap with longline fishing effort. Data suggest that the Atlantic probably consists of two regional management units: northern and southern (the latter including turtles breeding in South Africa). Although turtles and fisheries show highly diverse distributions, we highlight nine areas of high susceptibility to potential bycatch (four in the northern Atlantic and five in the southern/equatorial Atlantic) that are worthy of further targeted investigation and mitigation. These are reinforced by reports of leatherback bycatch at eight of these sites. International collaborative efforts are needed, especially from nations hosting regions where susceptibility to bycatch is likely to be high within their exclusive economic zone (northern Atlantic: Cape Verde, Gambia, Guinea Bissau, Mauritania, Senegal, Spain, USA and Western Sahara; southern Atlantic: Angola, Brazil, Namibia and UK) and from nations fishing in these high-susceptibility areas, including those located in international waters.

Building G20 outreach: The role of transnational policy networks in sustaining effective and legitimate summitry

G20 outreach processes, in the form of the Think 20, Labour 20, Business 20, and Civil 20, Youth 20, and Women 20, are a formal attempt by G20 leaders to engage various social sectors with G20 policymaking. This essay contends that G20 outreach processes are best understood as transnational policy networks, which are involved in widening the field of policy communication and deliberation. The importance of these transnational policy networks rest upon their role in developing and disseminating G20 policy priorities and principles; and are an attempt to enhance the legitimacy and influence of the G20 and its policy proposals.

"We agree that, in order to strengthen its ability to build and sustain the political consensus needed to respond to challenges, the G20 must remain efficient, transparent and accountable. To achieve this, we decide to … pursue consistent and effective engagement with non-members, regional and international organisations, including the United Nations, and other actors, and we welcome their contribution to our work as appropriate. We also encourage engagement with civil society.G20 Cannes Summit Final Declaration 2011 (G20 2011)"

The difficulty in balancing the effectiveness and representativeness of the Group of Twenty (G20) has led to sustained questions about its legitimacy (Cooper 2010; Rudd 2011; Cooper and Pouliot 2015). Consequently, while leaders have long sought external advice about the agendas of Group of Seven (G7) summits since 1975, and about the G20 finance ministers and central bank governors’ meetings (G20 FM/CBG) since 1999, there has been intensification, elaboration, and institutionalization of transnational networks of policymakers with respect to the G20 in recent years. These networks are especially evident in the form of the G20 working groups and G20 outreach processes involved in the G20 FM/CBG and the G20 leaders’ forum created in 2008.

G20 working groups include transgovernmental groups of government officials and outside experts within a specific policy area who are charged with preparing material for G20 deliberations. G20 outreach processes are a recent and more formal attempt by G20 leaders to engage various social sectors with the policymaking activity of the G20 and were first considered by the G20 membership in 2010 with a more formal engagement with business interests. This led to the formal development of G20 outreach groups in 2013 in the form of the Think 20 (think tanks), Labour 20, Business 20, Civil 20 and Youth 20, which include representatives from these sectors. In 2015, a Women 20 outreach group was also added. These outreach processes are best understood as transnational policy networks which have been built to support the G20’s capacity to be effective and legitimate.

This essay focuses on G20 outreach processes and examines why and how the G20 has sought to augment its intergovernmental summitry and transgovernmental working groups with transnational policy networks, purposely involving a range of societal interests. Transnational policy networks demonstrate the existence of policymaking practices which include the policy influence of experts and advocates outside government. These networks also indicate the ways in which governments, International Governmental Organizations (IGOs) and summits like the G20 engage society, or where elements of society engage themselves with the policymaking process (Stone 2008). These networks intersect with the intergovernmental activities of leaders and key diplomats, and overlap with the transgovernmental relationships of various levels of government bureaucrats (Baker 2009). One of the principle features of transnational policy networks is the way they create and channel the communication of political ideas and priorities. However, it is important to keep in the mind the purpose and power of actors involved in the network and consider who has the discretion and motivation to create the network in the first instance. As the G20 members stated in 2012, the aspiration for outreach is founded upon an intent to strengthen the G20’s capacity “to build and sustain the political consensus”. Consequently, it is important to consider how the development of transnational policy networks in the form of G20 outreach processes are able to sustain the effectiveness and legitimacy of the G20.

This essay contends that G20 outreach processes are best understood as transnational policy networks. These networks have been built to widen the field of policy communication and deliberation. Furthermore, these outreach processes and networks are an attempt to enhance the legitimacy and influence of the G20 and its policy proposals. While there is no doubt that outreach practices are “ad hoc responses to the widespread charge that the G20 reproduces the politics of exclusion in global governance” (Cooper and Pouliot 2015, 347), these practices have the potential to improve both the effectiveness and legitimacy of the G20. The G20 possesses uncertain legitimacy and members of the G20 demonstrate an awareness of this and a corresponding willingness to actively develop various political practices to support the capacity and legitimacy of the G20.

However, G20 outreach also enables the G20 to place some limit upon the policy narratives and ideas that develop within these policy networks. The G20 is liable to be misunderstood without examining the activity of these transnational networks because the G20 is fundamentally a deliberative policy forum rather than a negotiating forum of binding regulations. Transnational policy networks have the potential to scrutinize and amplify relevant policy ideas and thereby enhance the legitimacy of the G20 and strengthen the capacity of the G20 to address an array of global economic and social problems. However, while some narrative control is important to amplify the G20 agenda, too much narrative control will undermine its legitimacy and capacity to develop broad-based responses to global problems. This essay explores the formation of these transnational policy networks by first outlining the evolution of the purpose and configuration of the G20, then it considers the ways G20 outreach processes constitute transnational policy networks and why they have been established, and lastly, analyses how these networks operate to enhance the legitimacy and effectiveness of the G20.

The influence of temperature on the forming behavior of metal/polymer laminates in sheet metal forming

The influence of temperature on the forming behavior of an aluminum/polypropylene/aluminum (APA) sandwich sheet was studied. Shear and tensile tests were performed to determine the mechanical properties of the laminate and the component materials as a function of process temperature. The forming limit diagram (FLD) of the laminate was established for two different temperatures, and its springback behavior was examined in four-point bend and channel bend tests. Cup forming tests were performed at various test temperatures to determine the limiting drawing ratio (LDR) and the tendency for wrinkling at these temperatures. Although there was only a minor influence of temperature on the mechanical properties and the FLD values of the laminate, the bend test results reveal that springback can be reduced by forming at higher temperature. The decreasing strength of the core material with rising process temperature led to an increased tendency of the laminate to wrinkle in the heated cup drawing tests.

Population dynamics of the infaunal bivalve, Soletellina alba

The population dynamics of the infaunal bivalve Soletellina alba was investigated at three sites situated within close proximity to the mouth of the Hopkins River estuary. The initial study design was planned to examine the importance of winter flooding to the persistence of this bivalve mollusc within the Hopkins estuary, since mass mortalities have been observed during previous years coincident with periods of winter flooding. Unfortunately, the climatic conditions experienced during this study were atypical compared to the long-term average, so detailed sampling was limited to two, unanticipated, non-flood years rather than two, highly anticipated, flood years. This hampered my ability to conduct complete tests of the importance of winter flooding. Patterns of river discharge and the frequency and duration of mouth opening and closing differed greatly from that expected. Unexpectedly, periods of mouth closure were not always associated with periods of minimal river discharge; low salinities were another unexpected result during an extended period of mouth closure during 1998. As expected, salinities varied considerably with increasing water depth when the estuary mouth was open. Mouth closure lead to salinities becoming more uniform between water depths but hypoxic and anoxic conditions became evident via stratification in the water column at 1 m below the Australian Height Datum (AHD). Other than trends associated with increased water depth, significant variation was not evident between measurements of salinity taken from three sites within close proximity of the estuary mouth (approximately 500 m), or during changes in tide. The most pertinent anomaly was the absence of winter flooding. The distribution and abundance of juvenile and adult S. alba was variable across all Dates, Sites and Channel elevations (i.e. water depths) sampled during this study. An experimental test comparing the recruitment of juveniles at different channel elevations and in sediments of varying particle size was conducted during an exceptionally successful period of recruitment during 1999. The results of these tests showed that recruitment was greatest at the shallowest channel elevation used, and there was little evidence that sediment particle size influenced recruitment. In contrast to 1999, recruitment during 1997 or 1998 was extremely poor. Growth rates were monitored using tagged individuals held in caged and uncaged plots, which revealed that growth was highly variable among individuals, but not between Sites. These tests also revealed that growth was negligible during the colder, winter months, and that the fastest growing individuals were capable of growing 0.2 mm/day. Mixed results were obtained for tests of potential cage artifacts and the influence of handling. Caging and differing amounts of handling did not appear to influence growth, but there was evidence that cages and handling influenced bivalve condition and number of mortalities. These direct tests appeared to be the most appropriate method for determining growth rates of this species, since attempts to analyse length-frequency data were made difficult by the apparent convergence of cohorts, and shell aging is difficult due to the thin, fragile nature of the shell. As expected, mass mortalities were observed during the flood of 1996, but not during the two non-flood years of 1997 and 1998. There were, however, some considerable declines in abundances at some channel elevations during the two non-flood years. However, these declines were attributable to the complete disappearance of individuals, rather than the sudden presence of numerous, recently dead individuals that typify observed declines during winter flooding. The complete disappearance of individuals suggest that S. alba may be capable of post-settlement emigration, or that they were consumed by an unknown predator. Salinity tolerance tests showed that bivalves exposed to low salinities (≤6 ppt), exhibited poorer condition and took longer to re-burrow into sediments than those exposed to greater salinities (≥14 ppt), while death of bivalves exposed to salinities ≤1 ppt occurred after 8 days of exposure. These tests provide evidence that low salinities are probably the principal cause of mass mortalities during winter flooding, although the interaction between salinity, temperature and turbidity also deserve consideration. The results of this study indicate that certain aspects of winter flooding, especially salinity, are responsible for the mass mortalities of S. alba rather than the result of a short-lived life history. I hypothesise that the survival of very young juveniles (between 0.5 and 1 mm shell length) and rapid growth rates are important features of the life history of S. alba that explain its successful persistence within the Hopkins River estuary. The rapid rates of growth suggest that it may be possible for juveniles that survive winter flooding to grow, reach sexual maturity, and reproduce before the onset of the next flood event. Unfortunately, the increased survivorship of juveniles during periods of winter flooding was not demonstrated by this study because of the absence of winter flooding and also relatively poor recruitment. It is highly likely that this species is capable of completing it entire life cycle within the estuary since the absence of other nearby populations, together with periods of mouth closure, are likely to greatly limit the potential contribution made by larvae entering from the surrounding marine environment. This study has added considerably to our knowledge of how infauna cope with life in the intermittently closing estuaries that typify semi-arid coastlines in the Southern Hemisphere.

Charting changes in the discipline : a tri-continental analysis

The purpose of this paper is to describe and chart three key and underpinning dimensions of Information Systems (IS) research in three ‘flagship’ journals of three continents, over a period of nine years. The dimensions are: research domain, research paradigm, and research setting and they comprise respectively, ‘the what’, ‘the how’, and ‘the where’ of research. The paper contributes to the debate on research diversity in Information Systems in three ways. Firstly, it provides a view of ‘research domain’ that is at a semantically higher level than previous schemas examining the ‘what’ of research. This view reveals deep structural trends within the IS literature. Secondly, it details the results of a content analysis which examined research domain, research paradigm, and research setting within the journals MIS Quarterly (MISQ), European Journal of Information Systems (EJIS) and the Australasian Journal of Information Systems (AJIS) during the years 2001-2009. Lastly, the study compares the publication trends across the three continents and identifies an emerging, if tentative convergence across the Atlantic and to some extent in Australia. The paper suggests some reasons for this convergence and some avenues to explore it.

The importance of sand albedo for the thermal conditions on sea turtle nesting beaches

At Ascension Island and Cyprus, major nesting areas for green turtles (Chelonia mydas) in the Atlantic and Mediterranean, respectively, visual inspection shows some beaches are light in colour while others are darker. We objectively measured the albedo of the sand on different beaches, i.e. the percentage of the incident solar radiation that was reflected from the sand surface. At sites where albedo was recorded, we also measured the temperature of the sand at nest depths. At both rookeries, the sand temperature was markedly higher on darker beaches due to greater absorption of the incident solar radiation over the diurnal cycle. Temperature loggers buried at nest depths revealed seasonal changes in temperature on both islands, but showed that the lowest temperatures found on the darker beaches rarely dropped below the highest temperatures on the lighter beaches. Sea turtles exhibit temperature-dependent sex determination. Since sand albedo is a major avenue for the production of a range of incubation temperatures on both islands, it will also have profound implications for hatchling sex ratios. In comparison with both Ascension Island and Cyprus, for samples collected from sea turtle rookeries around the world there was an even greater range in sand albedo values. This suggests that sand albedo, a factor that has previously received little consideration, will have profound implications for nest temperatures, and hence hatchling sex ratios, for other populations and species.