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Low-complexity ultrasound systems are increasingly desired for both wearable, point-of-care ultrasound and high-end massive-channel ultrasound for 3-D matrix imaging. However, the imaging capabilities, including spatial resolution and contrast, could suffer as low complexity systems are pursued, which remains as an unresolved tradeoff. To mitigate this limitation, this study revisits the general structures of analog and digital beamformers and introduces a hybrid approach, referred to as analog-digital hybrid beamforming, to implement efficient ultrasound systems. The suggested hybrid beamforming takes two stages sequentially, where the first analog stage partially beamforms M-channel RF signals to N sum-out data (i.e., M-to-N beamforming), and the second digital stage beamforms N partial sums to single final beamformed data (i.e., N-to-1 beamforming). Our approach was systematically designed and implemented with only four major integrated circuits, which was capable of driving full 64-channel transmission and reception. The developed system was demonstrated with a customized 64-channel 1-D phased array using a commercial tissue mimicking phantom. From the phantom imaging results, signal-to-noise ratio, contrast-to-noise ratio, and full beam width at half maximum values were quantitatively evaluated. The demonstrated results indicate that the analog-digital hybrid beamforming can be applied to any type of array for sophisticated 3-D imaging and tiny wearable ultrasound applications. [ABSTRACT FROM AUTHOR]

In order to improve the satisfaction of online retail consumers and explore the process of forming consumer loyalty during the COVID-19 pandemic, this research combines the theories of perceived value and affect-as-information, taking cold chain logistics services (PDS) as an example to discuss the influence of PDS quality (PDSQ) of online retail cold chain on consumers' psychological emotion (satisfaction and psychological distress), attitude, and behaviour (loyalty). We collected 350 valid responses from an online response team in Wuhan, China, and analysed the data using exploratory factor analysis and structural equation modelling. Results reveal that the general psychological distress of consumers plays an intermediary role in the influence path of PDSQ on consumer loyalty during the pandemic. Therefore, online retailers should combine logistics services with measures to alleviate consumer psychological distress in disaster situations, which can increase consumers' loyalty to online retailers. [ABSTRACT FROM AUTHOR]