15 research outputs found

    Coordinating Complementary Waveforms for Sidelobe Suppression

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    We present a general method for constructing radar transmit pulse trains and receive filters for which the radar point-spread function in delay and Doppler, given by the cross-ambiguity function of the transmit pulse train and the pulse train used in the receive filter, is essentially free of range sidelobes inside a Doppler interval around the zero-Doppler axis. The transmit pulse train is constructed by coordinating the transmission of a pair of Golay complementary waveforms across time according to zeros and ones in a binary sequence P. The pulse train used to filter the received signal is constructed in a similar way, in terms of sequencing the Golay waveforms, but each waveform in the pulse train is weighted by an element from another sequence Q. We show that a spectrum jointly determined by P and Q sequences controls the size of the range sidelobes of the cross-ambiguity function and by properly choosing P and Q we can clear out the range sidelobes inside a Doppler interval around the zero- Doppler axis. The joint design of P and Q enables a tradeoff between the order of the spectral null for range sidelobe suppression and the signal-to-noise ratio at the receiver output. We establish this trade-off and derive a necessary and sufficient condition for the construction of P and Q sequences that produce a null of a desired order

    Signal design for active sensing

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    2014 Summer.To view the abstract, please see the full text of the document

    Extensions to the Theory of Widely Linear Complex Kalman Filtering

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    Prominent Conductor Mechanism-Induced Electron Transfer of Biochar Produced by Pyrolysis of Nickel-Enriched Biomass

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    Biochar is redox-active and can function as a sustainable electron shuttle in catalyzing relevant redox reactions. It plays a crucial role in environmental remediation. In this work, we used different-nickel (Ni)-level biochars produced by the pyrolysis of plant biomass with correspondingly different Ni levels as extracellular electron shuttles for microbial reduction of ferrihydrite by Shewanella oneidensis MR-1. A high Ni level of the precursor considerably enhanced the conductor mechanism of the produced biochar and thus enabled the biochar to catalyze increased microbial reductions of the Fe(III) mineral, but it did not promote the charging and discharging capacities of the produced biochar. This study can aid in the search for natural biomass with high Ni content to establish low-cost biochars with wide-ranging applications in catalyzing the redox-mediated reactions of pollutants

    Accelerated Microbial Reduction of Azo Dye by Using Biochar from Iron-Rich-Biomass Pyrolysis

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    Biochar is widely used in the environmental-protection field. This study presents the first investigation of the mechanism of biochar prepared using iron (Fe)-rich biomass and its impact on the reductive removals of Orange G dye by Shewanella oneidensis MR-1. The results show that biochars significantly accelerated electron transfer from cells to Orange G and thus stimulated reductive removal rate to 72–97%. Both the conductive domains and the charging and discharging of surface functional groups in biochars played crucial roles in the microbial reduction of Orange G to aniline. A high Fe content of the precursor significantly enhanced the conductor performance of the produced biochar and thus enabled the biochar to have a higher reductive removal rate of Orange G (97%) compared to the biochar prepared using low-Fe precursor (75%), but did not promote the charging and discharging capacity of the produced biochar. This study can prompt the search for natural biomass with high Fe content to confer the produced biochar with wide-ranging applications in stimulating the microbial reduction of redox-active pollutants

    Molecular-weight-dependent redox cycling of humic substances of paddy soils over successive anoxic and oxic alternations

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    Humic substances (HSs) are critical to regulating methane cycling in temporary anoxic systems because their redox-active functional groups can sustainably shuttle electrons from microorganisms to oxygen (O-2) over successive anoxic and oxic alternations. Whether the relative amount of these redox-active functional groups involved in redox cycles is associated with the overall chemical structures of HS still remains poorly understood. In this study, variations in the reducing capacities (RCs) of HSs extracted from paddy soils were monitored over consecutive cycles of reduction by iron-reducing microorganisms and oxidation by O-2. Our results show that about 10-40% of the microbially reduced redox-active moieties within HS, which were reoxidised by O-2, cannot restore the same redox state as those before microbial reduction. The restoration extents of RCs of HSs after microbial reduction and O-2 reoxidation were greatly negatively correlated with average molecular weight (AMW). The microbially reduced HSs having large AMWs (>1,000 Da) were more kinetically difficult to restore by O-2 from a reduced state to an oxidised state than were those having small AMWs (<1,000 Da) possibly because the former, which underwent process of microbial reduction and O-2 reoxidation, were more easily sheltered by other parts of HS structures than were the latter. Nevertheless, the unsheltered redox-active groups that accounted for about 50-85% in HSs can be fully reversible and sustainable to switch between a reduced state and an oxidised state over successive redox cycles. Our results can help to understand the redox dynamics of HSs in biogeochemical cycles in environments