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1. Understanding and mitigating the impact of passing ships on underwater environmental estimation from ambient sound

   https://doi.org/10.1121/10.0035643  

   Lipor, John; Gebbie, John; Siderius, Martin (February 2025, The Journal of the Acoustical Society of America)

   We investigate the impact of low-rank interference on the problem of distinguishing between two seabed types using ambient sound as an acoustic source. The resulting frequency-domain snapshots follow a zero-mean, circularly-symmetric Gaussian distribution, where each seabed type has a unique covariance matrix. Detecting changes in the seabed type across distinct spatial locations can be formulated as a two-sample hypothesis test for equality of covariance, for which Box's M-test is the classical solution. Interference sources such as passing ships result in additive noise with a low-rank covariance that can reduce the performance of hypothesis testing. We first present a method to construct a worst-case interference field, making hypothesis testing as difficult as possible. We then provide an alternating optimization procedure to recover the interference-free covariance matrix. Experiments on synthetic data show that the optimized interferer can greatly reduce hypothesis testing performance, while our recovery method perfectly eliminates this interference for a sufficiently small interference rank. On real data from the New England Shelf Break Acoustics experiment, we show that our approach successfully mitigates interference, allowing for accurate hypothesis testing and improving bottom loss estimation. 

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2. Real-time photonic blind interference cancellation

   https://doi.org/10.1038/s41467-023-43982-w  

   Lederman, Joshua C.; Zhang, Weipeng; de Lima, Thomas Ferreira; Blow, Eric C.; Bilodeau, Simon; Shastri, Bhavin J.; Prucnal, Paul R. (December 2023, Nature Communications)

   Abstract mmWave devices can broadcast multiple spatially-separated data streams simultaneously in order to increase data transfer rates. Data transfer can, however, be compromised by interference. Photonic blind interference cancellation systems offer a power-efficient means of mitigating interference, but previous demonstrations of such systems have been limited by high latencies and the need for regular calibration. Here, we demonstrate real-time photonic blind interference cancellation using an FPGA-photonic system executing a zero-calibration control algorithm. Our system offers a greater than 200-fold reduction in latency compared to previous work, enabling sub-second cancellation weight identification. We further investigate key trade-offs between system latency, power consumption, and success rate, and we validate sub-Nyquist sampling for blind interference cancellation. We estimate that photonic interference cancellation can reduce the power required for digitization and signal recovery by greater than 74 times compared to the digital electronic alternative. 

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3. Wideband Array Signal Processing with Real-Time Adaptive Interference Mitigation

   https://doi.org/10.3390/s23146584  

   Whipple, Adam; Ruzindana, Mark W; Burnett, Mitchell C; Kunzler, Jakob W; Lyman, Kayla; Jeffs, Brian D; Warnick, Karl F (July 2023, Sensors)

   Wideband beamforming and interference cancellation for phased array antennas requires advances in signal processing algorithms, software, and specialized hardware platforms. A high-throughput array receiver has been developed that enables communication in radio frequency interference-rich environments with field programmable gate array (FPGA)-based frequency channelization and packetization. In this study, a real-time interference mitigation algorithm was implemented on graphics processing units (GPUs) contained in the data pipeline. The key contribution is a hardware and software pipeline for subchannelized wideband array signal processing with 150 MHz instantaneous bandwidth and interference cancellation with a heterogeneous, distributed, and scaleable digital signal processing (DSP) architecture that achieves 30 dB interferer cancellation null depth in real time with a moving interference source. 

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4. Niche differentiation, reproductive interference, and range expansion

   https://doi.org/10.1111/ele.14350  

   Grether, Gregory F.; Finneran, Ann E.; Drury, Jonathan P. (December 2023, Ecology Letters)

   Abstract Understanding species distributions and predicting future range shifts requires considering all relevant abiotic factors and biotic interactions. Resource competition has received the most attention, but reproductive interference is another widespread biotic interaction that could influence species ranges. Rubyspot damselflies (Hetaerinaspp.) exhibit a biogeographic pattern consistent with the hypothesis that reproductive interference has limited range expansion. Here, we use ecological niche models to evaluate whether this pattern could have instead been caused by niche differentiation. We found evidence for climatic niche differentiation, but the species that encounters the least reproductive interference has one of the narrowest and most peripheral niches. These findings strengthen the case that reproductive interference has limited range expansion and also provide a counterexample to the idea that release from negative species interactions triggers niche expansion. We propose that release from reproductive interference enables species to expand in range while specializing on the habitats most suitable for breeding. 

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5. Localized Momentum-Space Distribution of Photocurrents Injected by Quantum Interference of Nonlinear Absorption Processes

   https://doi.org/10.1364/FIO.2023.JTu5A.32  

   Gong, Yiming; Wang, Kai; Cundiff, Steven T. (January 2023, Optica Publishing Group)

   Based on polarization dependence, we show that momentum-space distribution of photocurrents is more localized in quantum interference of two- and three-photon absorptions than that in quantum interference of one- and two-photon absorptions. 

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