A technique based on time-frequency and tomographic analysis to extract helicopter blade parameters for the purposes of radar non-cooperative target recognition (NCTR) is investigated. The proposed algorithm shows that (under certain conditions) it is feasible to extract the number, blade length, blade tip velocity and angular velocity of a helicopter's main rotor. Simulation results from a point scatterer model is validated through results on measured data from several different commercial helicopters. The developed technique is most suited to pulse-Doppler tracking radar and is shown to be feasible at a range of 11km with a radar not specifically designed for this purpose.
A novel Frequency Domain, Stepped Frequency Processing(FD-SFP) technique to obtain high radar range resolution was developed by AJ Wilkinson in 1997. Range resolution is directly related to the measurement bandwidth of a radar system. The FD-SFP technique pieces together several sub portions of the target scene reflectivity spectrum to form a high resolution radar range return. This paper demonstrates the use of the FD-SFP algorithm on the CSIR X-Band experimental SAR system (RoofSAR). Some issues arising in practical implementation of the technique are discussed. Results of using the technique on radar data recorded by the RoofSAR are presented. It is concluded that the technique provides a viable optlon for generating SAR imagery with high range resolution and an acceptable level of ghosting artifacts.
PLATES CLVIII-CLXIV INTEREST in the mycotoxins has been stimulated by numerous reports on the toxic effects of aflatoxin in experimental animals (Butler and Barnes, 1963;Butler, 1964; Newberne et ul., 1964) and by suggestions that these toxins offer a reasonable explanation for the occurrence of endemic liver cancer in Africa and comparable regions (OettlC, 1964). It is becoming increasingly apparent that mould metabolites besides aflatoxin cause significant pathological changes in experimental animals. A recent report from this laboratory indicates that twenty-two species of moulds recovered from domestic cereal and legume crops are toxic to ducklings (Scott, 1965). From one of these moulds, Aspergillus ochruceus Wilh., a toxin given the name of ochratoxin A, has been isolated in pure crystalline form (van der Merwe et al., 1965).It is the purpose of the present paper to describe ultrastructural and certain histochemical changes found in the liver cells of ducklings and rats after the administration of pure crystalline ochratoxin A in shortterm experiments.MATERIALS AND METHODS Thirty day-old Pekin ducklings (average weight 50 g.) and thirty weanling male Wistar rats (average weight 60 g.) were each given 100 pg. crystalline ochratoxin A dissolved in 0.5 ml. 0.1~-NaHC03 by stomach tube. Control animals (10 ducklings and 10 rats) were given an equivalent volume of sodium bicarbonate. The ducklings and rats were fed on chicken mash and stock rat ration respectively, and given water ad libitum throughout the experimental period.One experimental animal and one control from each experiment were killed by decapitation at intervals of 1, 2, 4, 8, 16 and 24 hr after administration of the toxin. All surviving animals were killed 72 hr after the start of the experiments.A portion of liver tissue obtained from the left lobe of the liver of each duckling and rat immediately after decapitation was divided into four blocks. Unfixed cryostat sections from one block were stained for succinic dehydrogenase (SDH) according to the nitro-BT method (Burstone, 1962). A second block was fixed in cold (4" C) formal-calcium (Baker, 1944-45) for 12-24 hr and frozen sections were incubated in the appropriate substrates at 37" C for the demonstration of alkaline phosphatase (AlkPase), acid phosphatase (AcPase), adenosine triphosphatase (ATPase), inosine diphosphatase (IDPase) and thiamine pyrophosphatase (TPPase) according to methods previously described (Theron, 1965). For electron microscopy a third cube was immersed in cold ( 0 ' 4 C) phosphate-buffered 1 per cent. osmium tetroxide (Millonig, 1962) and embedded in Epon 812 (Luft, 1961).
A combined Gaussian mixture model and hidden Markov model (HMM) is developed to distinguish between slow moving animal and human targets using mel-cepstrum coefficients. This method is compared to the state-ofthe-art in current micro-Doppler classification and an improvement in performance is demonstrated. In the proposed method, a Gaussian mixture model (GMM) provides a mixture of mel-frequency distributions while a hidden Markov model is used to characterise class specific transitions between the mel-frequency mixtures over time. A database of slow moving targets in a cluttered environment is used to evaluate the performance of the model. It is shown that the combined Gaussian mixture Hidden Markov model (GMM-HMM) approach can accurately distinguish between different classes of animals and humans walking in these environments. Results show that the classification accuracy of the model depends on the continuous observation time on target and ranges from 75% to approximately 90% for times on target between 250 ms to 1.25 s respectively. A confidence based rejection scheme is also presented to reduce false classification rates. Possible applications include border safeguarding and wildlife anti-poaching operations for species such as rhinos or elephants.
Autofocus is a well known required step in ISAR (and SAR) processing to compensate translational motion. This research proposes a time domain autofocus algorithm and discusses its relation to the well known phase gradient autofocus (PGA) technique. Results on simulated and measured data show that the algorithm performs well. Unlike many other ISAR autofocus techniques, the algorithm does not make use of several computationally intensive iterations between the data and image domains as part of the autofocus process. As such, the proposed algorithm could prove to be faster than other techniques. Observations are made regarding the type of phase errors that can be handled, and it is argued that the technique could be posed either as parametric or nonparametric depending on the type of phase errors expected.
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