2,753 research outputs found
Mapping Crop Cycles in China Using MODIS-EVI Time Series
As the Earth’s population continues to grow and demand for food increases, the need for improved and timely information related to the properties and dynamics of global agricultural systems is becoming increasingly important. Global land cover maps derived from satellite data provide indispensable information regarding the geographic distribution and areal extent of global croplands. However, land use information, such as cropping intensity (defined here as the number of cropping cycles per year), is not routinely available over large areas because mapping this information from remote sensing is challenging. In this study, we present a simple but efficient algorithm for automated mapping of cropping intensity based on data from NASA’s (NASA: The National Aeronautics and Space Administration) MODerate Resolution Imaging Spectroradiometer (MODIS). The proposed algorithm first applies an adaptive Savitzky-Golay filter to smooth Enhanced Vegetation Index (EVI) time series derived from MODIS surface reflectance data. It then uses an iterative moving-window methodology to identify cropping cycles from the smoothed EVI time series. Comparison of results from our algorithm with national survey data at both the provincial and prefectural level in China show that the algorithm provides estimates of gross sown area that agree well with inventory data. Accuracy assessment comparing visually interpreted time series with algorithm results for a random sample of agricultural areas in China indicates an overall accuracy of 91.0% for three classes defined based on the number of cycles observed in EVI time series. The algorithm therefore appears to provide a straightforward and efficient method for mapping cropping intensity from MODIS time series data
Canopy Cover Prediction From Stand Density Attributes: Stocking, Crown Width, and Overlap Functions
The goals for a wide range of forest management objectives are often stated in terms of the amount and layering of canopy cover. However, measuring canopy cover is labor intensive and different techniques provide widely different estimates. Several approaches have been developed to predict cover from common tree or stand-level density attributes, with varying results. This study used line-intercept measured tree cover from 1,424 Forest Inventory and Analysis (FIA) plots across Oregon to build predictive models from estimates of tree stocking, crown width, and other stand attributes (mean diameter, stand height, SDI, etc.). A variety of adjustments were applied to adjust for tree social status and account for tree crown overlap. Stocking was a better predictor of cover than crown width, although much of the error in the latter was due to estimates of crown overlap. The random crown overlap function that is standard in the Forest Vegetation Simulator (FVS) resulted in biased predictions in mesic forest types, but not in dry forest types. New model predictions based on stocking for mesic forest types were within 15 percent of measured cover for \u3e 82% of the observations. Although there are some additional options for improving estimated cover from tree and stand attributes, ground-based measurements will probably be required for precise estimates
The cycle must stop
Reports in recent years of thousands of Indians and Ladinos slaughtered in Guatemala and tens of thousands more fleeing their homes to refugee camps have provoked no outcry in the U.S. Popular resistance to the oppressive military regime is growing, yet President Reagan will ask to renew aid for the nation most notorious for human rights violations. This request should be denied and all support for this regime ended. The reasons should be clear when the Guatemala story is understood
Investigating physical and cognitive changes over two years in patients with moderate to late stage Parkinson’s Disease in Northumbria
Improved eBusiness Treasury Risk Management using Intelligent Agents: Increasing Returns, Controlling Risk
Following the global economic downturn and a collapse in international equity markets, many financial institutions and corporations have sought the higher returns associated with higher risk from trading in foreign exchange derivatives. These derivatives have become increasingly complex to the point where few specialists are able to accurately determine the level of exposure. Top traders seek high rewards for their successful investments. Rogue traders seek high rewards by concealing their unsuccessful gambling, sometimes to the extent of endangering the viability of their employers. Current technology copes poorly with dynamically changing business requirements and conditions so there is little technological support available for organizations sensitized by reports of rogue trading and increasingly obliged by financial regulators to improve their risk management practices. This paper proposes a risk management framework that can support FX derivative monitoring and trading based on the Williams-Elliot Agent Architecture. The framework uses agent technologies for improved management of treasury risk by continuous monitoring of all transactions across an organisation; continuous evaluation of exposures compared with prescribed parameters across an organisation; instantaneous reporting to senior management where trading begins to approach or violates the parameters. Rigorous examples of typical transactions illustrate how intelligent agents can be used to monitor risk and to make trades within a powerful risk modelling and management framework
The Dark Side of Making - Reflecting on Promises, Practices and Problems of the Last 25 Years
High Rate Digital Demodulator ASIC
The architecture of High Rate (600 Mega-bits per second) Digital Demodulator (HRDD) ASIC capable of demodulating BPSK and QPSK modulated data is presented in this paper. The advantages of all-digital processing include increased flexibility and reliability with reduced reproduction costs. Conventional serial digital processing would require high processing rates necessitating a hardware implementation in other than CMOS technology such as Gallium Arsenide (GaAs) which has high cost and power requirements. It is more desirable to use CMOS technology with its lower power requirements and higher gate density. However, digital demodulation of high data rates in CMOS requires parallel algorithms to process the sampled data at a rate lower than the data rate. The parallel processing algorithms described here were developed jointly by NASA's Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL). The resulting all-digital receiver has the capability to demodulate BPSK, QPSK, OQPSK, and DQPSK at data rates in excess of 300 Mega-bits per second (Mbps) per channel. This paper will provide an overview of the parallel architecture and features of the HRDR ASIC. In addition, this paper will provide an over-view of the implementation of the hardware architectures used to create flexibility over conventional high rate analog or hybrid receivers. This flexibility includes a wide range of data rates, modulation schemes, and operating environments. In conclusion it will be shown how this high rate digital demodulator can be used with an off-the-shelf A/D and a flexible analog front end, both of which are numerically computer controlled, to produce a very flexible, low cost high rate digital receiver
Saliva and Meningococcal Transmission
Neisseria meningitidis carriage was compared in swab specimens of nasopharynx, tonsils, and saliva taken from 258 students. We found a higher yield in nasopharyngeal than in tonsillar swabs (32% vs. 19%, p<0.001). Low prevalence of carriage in saliva swabs (one swab [0.4%]) suggests that low levels of salivary contact are unlikely to transmit meningococci
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