arXiv subjects

Zhengwu Wang

Publications and source records attributed to Zhengwu Wang.

3 recordsLinked to original sources

arXiv2026

System noise temperature measurements of a 19-element phased array feed

We present multi-epoch system noise temperature measurements of a 19 element hexagonal room-temperature phased array feed (PAF) using a modified Y-factor method. A Python-based pipeline with iterative channel calibration and maxSNR beam forming is developed to do data reduction, and a covariance-based decomposition scheme is proposed to extract mutual coupling noise temperature Tmc. Long-term observations from March to June 2026 capture temporal receiver noise drift mainly induced by LNA temperature variations. Within the 1.37-1.47 GHz operating band, the measured beam equivalent system noise temperature of the PAF is about 73-89 K. The measured Tmc baseline ranges from about 2 K to 8 K, while under thermal loading, the resonant peak of Tmc can increase to more than 20 K. The baseline of Tmc is consistent with the S-parameter mea surements, which show the Tmc of the full array ranges less than 10.7 K. The baseline fluctuation of Tmc most likely arises from the superposition of thermal and non-thermal components of the spatial electromagnetic fields. A detachable stainless steel shield is deployed to quantify sidelobe spillover noise, and comparative tests show unshielded en vironmental interference increases receiver noise temperature by over 60 K. The proposed measurements and data processing framework provides a practical reference for noise per formance characterization of ground-based radio telescope PAF prototypes.

astro-ph.IM↗

arXiv2025

Modeling Surface Wave Propagation over Meniscus and Scattering by a Surface-piercing Barrier

Recent experiments have revealed that the meniscus formed near a surface-piercing barrier can significantly alter the propagation and scattering of capillary-gravity surface waves, beyond what classic flat-surface models predict. In particular, wave transmission increases as the barrier pulls up the meniscus, then drops sharply if the barrier is raised further, overturning the meniscus. Motivated by these findings, this paper develops two linearized theoretical frameworks that incorporate meniscus geometry and pinned contact line conditions into capillary-gravity wave propagation and scattering. Model~1 assumes a vertical wave perturbation of the unperturbed meniscus, thereby extending classic flat-surface boundary conditions in a relatively straightforward manner. Model~2 takes a more comprehensive approach, defining surface wave perturbations normal to the curved meniscus and reparameterizing boundary conditions in terms of arc length. While Model~1 proves convenient mathematically, it is restricted to single-valued meniscus shapes. By contrast, Model~2 is capable of describing multi-valued or overturning free surfaces, thereby capturing a wider range of physically realistic scenarios. Numerical simulations based on both models reproduce the experimental observations on how wave transmission varies with changes in meniscus height and contact angles as the barrier is lifted, underscoring the critical influence of meniscus curvature in small-scale wave-structure interactions. These results establish a robust theoretical foundation for predicting and optimizing capillary-gravity wave scattering in microfluidic, industrial, and scientific applications.

physics.flu-dyn↗

arXiv2025

Meniscus-Driven Modulation of Surface Wave Transmission Across Barriers

Meniscus oscillations at interfaces between liquids, solids, and air significantly impact fluid dynamics and control. While idealized models exist, experimental data on capillary-gravity wave scattering involving meniscus effects remain limited. In this study, we systematically measured wave transmission past a surface-piercing barrier, focusing on meniscus and contact-line effects. By varying the barrier's surface properties and the wave frequencies, we explored how meniscus deformation influences wave transmission. The results are compared with simulations and limiting-case theories. We find that the meniscus water column beneath the barrier enhances coupling and increases transmission, while surface bending suppresses it by constraining motion. These competing effects explain the observed frequency and contact angle dependencies. Our findings provide insights into how meniscus dynamics govern surface wave behavior.

physics.flu-dyn↗