Parallel Cyclostationarity-Exploiting Algorithm for Energy-Efficient Spectrum Sensing

The evolution of wireless communication systems leads to Dynamic Spectrum Allocation for Cognitive Radio, which requires reliable spectrum sensing techniques. Among the spectrum sensing methods proposed in the literature, those that exploit cyclostationary characteristics of radio signals are particularly suitable for communication environments with low signal-to-noise ratios, or with non-stationary noise. However, such methods have high computational complexity that directly raises the power consumption of devices which often have very stringent low-power requirements. We propose a strategy for cyclostationary spectrum sensing with reduced energy consumption. This strategy is based on the principle that p processors working at slower frequencies consume less power than a single processor for the same execution time. We devise a strict relation between the energy savings and common parallel system metrics. The results of simulations show that our strategy promises very significant savings in actual devices.

Evolução morfodinâmica da região de influência estuarina do Rio Curimataú/RN, com ênfase nas alternativas do ambiente deposicional de manguezal e a integração de geodados em Sig

The estuaries are important investigation zones of the actual morphodynamic and of depositional facies of recent geological history. They are constituted in important receptor means of the coastal area sediments, where the evolutionary processes occur quickly. They are also attractive means for the development of anthropic activities, which in a disordered way interfere in the active processes in the sedimentary balance of the coastal areas. Among the human interventions, the alterations of the depositional environment of mangroves in areas of tropical estuary is deserving relevance, whose implications for the environment estuarine and the coastal adjacent, they are still far to be known. Due to the interest of the sedimentologic component in the comprehension of the processes linked to the evolution of the environments estuarine and coastal adjacent, this work, aimed at the understanding of the morphodynamic coastal phenomena that comprise the region of estuarine influence of the River Curimataú / RN. It was also evaluated in the morphodynamic context the implications due to alterations of the depositional environment of mangrove by anthropic activity. The Curimataú Estuary, located in the south portion of the oriental coast of Rio Grande do Norte, in the last decades has been objective of the overwhelming occupation of the shrimp farm in areas of mangroves, which were implanted with perspectives of development in a short to medium period. On the other hand, the estuary and its region of coastal influence lacks enough information to subsidize the planning and reorganization more effective of the surrounding activities. Thus, it was intended with this work to give a contribution target tothe maintainable use of the coastal resources of this region. A series of studies using data of orbital and acoustic remote sensing, as of sediments sampling, were executed in the gutter of the estuary. The obtained results starting from the interpretation of bathymetric maps, echo sounder graphics and of distribution of sediments made possible the location of the estuary based in morpho-sedimentar criteria. The estuarine tidal flat was dissected in environments of intertidal mangroves, supratidal mangroves and apicuns with base in the integration of data of sensor optic and of radar following by the field control. The adjacent coast that is influenced by the Curimataú estuary, was segmented according to their geomorphologic characteristics, where each segment had a point of observation of the beach morphodynamic, during the period from january/2001 to february/2002. Once every month, beaches profiles, collections of sediments in the beach zones, as measurement of hydrodynamic parameters were executed. The results of the observations of the tidal environment showed that the area of estuarine influence of the Curimataú begins to suffer negative sedimentary taxes, where in some beaches, the erosive processes are already observed. The granulometric characteristics of the beach sediments start to tend for the increase of thin sand in the erosive periods. The destruction of the depositional environments of mangroves of the Curimataú estuary, to the construction of shrimp farms, can be providing the diminution of the tidal prism of the estuary, enlarging the effects of the local increasing of the sea level, through the smaller supplying of sediments to the adjacent coast. Besides this, it was verified the possibility of the sanding of the tidal channel in the margins of the destroyed areas of mangroves, where very high taxes of sedimentation of thin materials were estimated in case of these areas were preserve

Aquisição, processamento e análise de dados de sísmica de alta resolução na plataforma continental norte do Rio Grande do Norte: Vale inciso do rio açu

On the modern Continental Shelf to the north of Rio Grande do Norte state (NE Brazil) is located a paleo-valley, submerged during the last glacial sea-level lowstand, that marks continuation of the most important river of this area (Açu River). Despite the high level of exploration activity of oil industry, there is few information about shallow stratigraphy. Aiming to fill this gap, situated on the Neogene, was worked a marine seismic investigation, the development of a processing flow for high resolution data seismic, and the recognition of the main feature morphology of the study area: the incised valley of the River Açu. The acquisition of shallow seismic data was undertaken in conjunction with the laboratory of Marine Geology/Geophysics and Environmental Monitoring - GGEMMA of Federal University of Rio Grande do Norte UFRN, in SISPLAT project, where the geomorphological structure of the Rio paleovale Açu was the target of the investigation survey. The acquisition of geophysical data has been over the longitudinal and transverse sections, which were subsequently submitted to the processing, hitherto little-used and / or few addressed in the literature, which provided a much higher quality result with the raw data. Once proposed for the flow data was developed and applied to the data of X-Star (acoustic sensor), using available resources of the program ReflexW 4.5 A surface fluvial architecture has been constructed from the bathymetric data and remote sensing image fused and draped over Digital Elevation Models to create three-dimensional (3D) perspective views that are used to analyze the 3D geometry geological features and provide the mapping morphologically defined. The results are expressed in the analysis of seismic sections that extend over the region of the continental shelf and upper slope from mouth of the Açu River to the shelf edge, providing the identification / quantification of geometrical features such as depth, thickness, horizons and units seismic stratigraphyc area, with emphasis has been placed on the palaeoenvironmental interpretation of discordance limit and fill sediment of the incised valley, control by structural elements, and marked by the influence of changes in the sea level. The interpretation of the evolution of this river is worth can bring information to enable more precise descriptions and interpretations, which describes the palaeoenvironmental controls influencing incised valley evolution and preservation to provide a better comprehensive understanding of this reservoir analog system

Caracterização de processos morfodinâmicos e hidrodinâmicos do cinturão lacustre meridional da Reserva Biológica do Lago Pirituba, Amapá

The Amapá State has an important natural lake system, known as The Amapá Lakes Region . Most of these lakes are on the southern part of Amapá s coastal plain, which has 300 km of extension and it s composed by holocenic sediments deposited at the northern part of Amazon River to the Orange Cape located on the northern part of Amapá state. This region is under influence of the Amazon River discharge which is the largest liquid discharge of about 209.000 m³/s and biggest sediment budget discharged on the ocean in the order 6.108 ton per day. The climate is influenced by the Intertropical Convergence Zone and El Niño Southern Oscillation which act mainly under precipitation, nebulosity, local rivers and tidal hidrology. In this region lake belts are Ocidental, Oriental and Meridional Lake Belts. The last one is formed by the by the lakes Comprido de Cima, Botos, Bacia, Lodão, Ventos, Mutuco and Comprido de Baixo. These lakes are the closest to the Araguari River and are characterized by pelitic sedimentation associated with fluvial and estuarine flood plains under influence of tides. The lakes are interconnected, suffer influence of flood pulses from the Tartarugal, Tartarugalzinho and Araguari rivers and the hydrodynamic and morphodynamic know edge is poor. Volume and area reduction, natural eutrophication, anthophic influence, hidrodynamic alterations, morphological changes and are factors which can contribute to the closing of such lakes on the Meridional Lake Belt. This belt is inside the boundaries of the Biological Reserve of Piratuba Lake, created in 1980 for integral protection. Due to the fragility of the environment together with the poor knowledge of the system and with the study area relevancy it is necessary to know the hydrodynamic and geoenvironmental processes. This work aims the characterization of morphodynamic and hydrodynamic processes in order to understand the geoambiental context of the Meridional Lake Belt, from the Comprido de Baixo Lake to the dos Ventos Lake, including the Tabaco Igarape. Methodology was based on the hydrodynamic data acquisition: liquid discharge (acoustic method), tides, bathymetry and the interpretation of multitemporal remote sensing images, integrated in a Geographic Information System (GIS). By this method charts of the medium liquid discharges of Lake Mutuco and Tabacco Igarape the maximum velocity of flow were estimated in: 1.1 m/s, 1.6 m/s and 1.6 m/s (rainy season) and 0.6 m/s, 0.6 m/s and 0.7 m/s (dry period), the maximum flow in: 289 m³/s, 297 m³/s and 379 m³/s (rainy season) and 41 m³/s , 79 m³/s and 105 m³/s (dry period), respectively. From the interpretation of multitemporal satellite images, maps were developed together with the analysis of the lakes and Tobaco Igarape evolution from 1972 to 2008, and were classified according to the degree of balance in the area: stable areas, eutrophic areas, areas of gain, and eroded areas. Troughout analysis of the balance of areas, it was possible to quantify the volume of lake areas occupied by aquatic macrophytes. The study sought to understand the hydrodynamic and morphodynamic processes occurring in the region, contributing to the elucidation of the processes which cause and/or favor geoenvironmental changes in the region; all such information is fundamental to making the management of the area and further definition of parameters for environmental monitoring and contributing to the development of the management plan of the Biological Reserve of Lake Piratuba. The work activities is a part of the Project "Integration of Geological, geophysical and geochemical data to Paleogeographic rebuilding of Amazon Coast, from the Neogene to the Recent