On the use of multiple antenna arrays and corner reflector assemblies in radio positioning applications

Modern radio positioning systems often use multiple-antenna arrays or corner reflector arrays in order to increase the system range. A theoretical investigation of the movement of the antenna phase center on these arrays is carried out, and the resulting distance error is presented for several array configurations.     

Crisis? What crisis? Displacing the spatial imaginary of the fiscal state

This paper argues that there is an immanent and evolving relationship between the prevailing form of taxation and the economic geographies of the state. Despite this, the geographic significance of taxation has been obscured by the language in which its historic transformation tends to be couched. Prevailing fiscal systems tend to be presented as essentially static – institutionally and spatially fixed and routinely inscribed within the fixed boundaries and territories of the ‘sovereign’ fiscal state. Any threat to, or change in the nature or geography of the fiscal state tends to be couched in terms of ‘crisis’ – of negative and discontinuous change. This paper contends that these related and essentially conservative discourses of fiscal geography mask the degree to which fiscal spaces are both multiple and continuously evolving. More importantly, it argues, this fluidity and multiplicity does not threaten the stability and viability of state form, but it is an essential process in its maintenance and reproduction. Running counter to the prevailing discourse of the ‘national economy’, the practice of fiscal geography is an under-analysed but key aspect of the historical evolution and transformation of the imagined geographies of economies.     

Sedimentology and event timing of a catastrophic volcaniclastic mass flow,Volcan Hudson,Southern Chile

Eruption of Volcan Hudson, Aisen region, Southern Chile on 12 August 1971 melted up to 80% of ice within the 9-km-wide Hudson Caldera. Rapid mobilisation of abundant fluvio-glacial sediment within the adjacent Huemules valley led to the generation of a catastrophic mass flow which swept westwards along the valley, eventually entering the fjord some 40 km downstream. The mass flow, developing from one source and being unaffected by tributary input, was characterised by three events within the flood hydrograph: (1) a precessional flood possibly linked to breakage of an early formed dammed lake; (2) a main mass flow which varied in its rheological behaviour from plug-flow to hyperconcentrated flow; and (3) a recessional flood at the tail of the main flow which diluted towards a concentrated streamflow. The main debris flow displayed characteristics of pulsing, internal segregation/density stratification, significant downstream sediment assimilation, cohesive/frictional freezing with ensuing fluidisation and development of an advancing runout phase. Consideration of these sedimentary characteristics and spatial/temporal flow transformations are used to propose a schematic model of event timing within this catastrophic volcaniclastic flow.     

Distribution and seasonal abundance of large cetaceans in the Durban whaling grounds off KwaZulu-Natal,South Africa, 1972–1975

Daily charts of the aerial search effort (432 206 nautical miles) of the Union Whaling Company and 1 099 sightings of 10 497 whales were available from 628 flights off Durban between 1972 and 1975. Densities of whales were analysed by month and water depth distribution over the four-year period. Low observed densities of blue Balaenoptera musculus, right Eubalaena australis, sei B. borealis and humpback Megaptera novaeangliae whales most likely resulted from earlier whaling pressure. Seasonality of blue, sei and humpback whales was bimodal, indicative of winter migrations to the north of the Durban whaling grounds, whereas the unimodal seasonality of fin whales B. physalus and minke whales B. bonaerensis or B. acutorostrata suggest the offshore region as the northern terminus of their migrations. Sperm whales Physeter macrocephalus migrate northwards offshore of the KwaZulu-Natal coast in autumn/early winter and southwards in late winter/spring, with larger males migrating later than the smaller males and females. Killer whale Orcinus orca presence was coincident with that of offshore minke whales and the southward migrations of other baleen whales, whereas densities of animals deemed as bottlenose whale Hyperoodon planifrons suggest strong early and late summer seasonal abundance in the offshore region. Such extensive surveys offshore of the KwaZulu-Natal coast are unlikely to be repeated; hence, data-extraction of whaling records provides a valuable source of seasonal and distributional information for marine management.     

Spatio-temporal distribution of dissolved inorganic carbon and net community production in the Chukchi and Beaufort Seas

As part of the 2002 Western Arctic Shelf–Basin Interactions (SBI) project, spatio-temporal variability of dissolved inorganic carbon (DIC) was employed to determine rates of net community production (NCP) for the Chukchi and western Beaufort Sea shelf and slope, and Canada Basin of the Arctic Ocean. Seasonal and spatial distributions of DIC were characterized for all water masses (e.g., mixed layer, halocline waters, Atlantic layer, and deep Arctic Ocean) of the Chukchi Sea region during field investigations in spring (5 May–15 June 2002) and summer (15 July–25 August 2002). Between these periods, high rates of phytoplankton production resulted in large drawdown of inorganic nutrients and DIC in the Polar Mixed Layer (PML) and in the shallow depths of the Upper Halocline Layer (UHL). The highest rates of NCP (1000–2850 mg C m⁻² d⁻¹) occurred on the shelf in the Barrow Canyon region of the Chukchi Sea and east of Barrow in the western Beaufort Sea. A total NCP rate of 8.9–17.8×10¹² g for the growing season was estimated for the eastern Chukchi Sea shelf and slope region. Very low inorganic nutrient concentrations and low rates of NCP (<15–25 mg C m⁻² d⁻¹) estimated for the mixed layer of the adjacent Arctic Ocean basin indicate that this area is perennially oligotrophic.     

On the jet contribution to the active galactic nuclei cosmic energy budget

Black holes release energy via the production of photons in their accretion discs but also via the acceleration of jets. We investigate the relative importance of these two paths over cosmic time by determining the mechanical luminosity function (LF) of radio sources and by comparing it to a previous determination of the bolometric LF of active galactic nuclei (AGN) from X-ray, optical and infrared observations. The mechanical LF of radio sources is computed in two steps: the determination of the mechanical luminosity as a function of the radio luminosity and its convolution with the radio LF of radio sources. Even with the large uncertainty deriving from the former, we can conclude that the contribution of jets is unlikely to be much larger than ∼10 per cent of the AGN energy budget at any cosmic epoch.