arXiv subjects

Songwen Xiao

Publications and source records attributed to Songwen Xiao.

5 recordsLinked to original sources

arXiv2026

Physical design of cold neutron direct geometry inelastic spectrometer at China Spallation Neutron Source

The Cold-Neutron Inelastic Spectrometer (CNIS) is a direct-geometry, time-of-flight instrument designed for China Spallation Neutron Source (CSNS) and optimized to probe low-energy lattice and magnetic excitations. The instrument integrates a long flight path with bent supermirror guides and an elliptical-focusing geometry to suppress high-energy background while improving cold-neutron delivery to the sample. A flexible multi-disk chopper suite provides pulse shaping, band selection and monochromatization, enabling multi-$E_\textrm{i}$ operation. Modular features, including an interchangeable high-focusing guide insert, radial collimation and a vacuum ``airbox'' for simplified sample-environment integration, enhance signal-to-noise and operational versatility. Through combined flight-path and chopper optimization, CNIS achieves excellent routine-mode energy resolution and can reach approximately $\sim 1\%$ in a dedicated high-resolution configuration. CNIS is planned to commence user operation in 2029, offering a highly flexible platform for cold-neutron inelastic scattering studies.

physics.app-ph↗

arXiv2023

Reverberation Time Control by Acoustic Metamaterials in a Small Room

In recent years, metamaterials have gained considerable attention as a promising material technology due to their unique properties and customizable design, distinguishing them from traditional materials. This article delves into the value of acoustic metamaterials in room acoustics, particularly in small room acoustics that poses specific challenges due to their significant cavity resonant nature. Small rooms usually exhibit an inhomogeneous frequency response spectrum, requiring higher wall absorption with specific spectrum to achieve a uniform acoustic environment, i.e., a constant reverberation time over a wide audible frequency band. To tackle this issue, we developed a design that simultaneously incorporates numerous subwavelength acoustic resonators at different frequencies to achieve customized broadband absorption for the walls of a specific example room. The on-site experimental measurements agree well with the numerical predictions, attesting to the robustness of the design and method. The proposed method of reverse-engineering metamaterials by targeting specific acoustic requirements has broad applicability and unique advantages in small confined spaces with high acoustic requirements, such as recording studios, listening rooms, and car cabins.

physics.app-ph↗

arXiv2020

Acoustic Metal

Metal reflects electromagnetic waves because of the large conductivity that is responsible for dissipation. During which the waves undergo a 180$^\circ$ phase change that is independent of the frequency. There is no counterpart material for acoustic waves. Here we show that by using an array of acoustic resonators with a designed high-density dissipative component, an "acoustic metal" can be realised that strongly couples with sound over a wide frequency range not otherwise attainable by conventional means. In particular, we show the acoustic Faraday cage effect that when used as a ring covering an air duct, 99% of the noise can be blocked without impeding the airflow. We further delineate the underlying volume requirement for an acoustic metal based on the constraint of the causality principle. Our findings complement the missing properties of acoustic materials and pave the way to the strong wave-material couplings that are critical for the applications as high-performance audio devices.

cond-mat.mtrl-sci↗

arXiv2017

Tunable Extremely Asymmetric Acoustic Metasurfaces Made by Coupled Membrane Resonators

We report the experimental demonstration of tunable asymmetric acoustic metasurfaces with extreme contrast, made by two decorated membrane resonators (DMRs) coupled via a sealed air column. The front side of the metasurface is impedance matched to air and perfectly absorbing, while the backside is hard and totally reflecting. When a suitable DC voltage is applied to the backside DMR with proper electrodes, the surface impedance of the back side of the metasurfaces can be tuned from one extreme to the other, such that the backside becomes impedance matched to air and totally absorbing, while the front side becomes perfectly reflecting. The metasurface also exhibits high transmission contrast around two frequencies. The tunability of the reflection is over 23 dB at 388 Hz, and that of the transmission is over 33 dB at 240 Hz and 590 Hz with 600 V of applied voltage. We further demonstrate one-side impedance matched metasurface with tunable working frequency 324.2 Hz to 335 Hz and reflection contrast over 31 dB.

physics.app-ph↗

arXiv2016

Hybrid membrane resonators for multiple frequency asymmetric absorption and reflection in large waveguide

We report that Hybrid membrane resonators (HMRs) made of a decorated membrane resonator backed by a shallow cavity can function as Helmholtz resonators (HRs) when mounted on the sidewall of a clear waveguide for air ventilation. When two single-frequency HMRs are used in the same scheme as two frequency-detuned HRs, asymmetric total absorption/reflection is demonstrated at 286.7 Hz with absorption coefficient over 97 % in a waveguide 9 cm x 9 cm in cross section. When two multiple-frequency HMRs are used, absorption in the range of near 60 % to above 80 % is observed at 403 Hz, 450 Hz, 688 Hz, 863 Hz and 945 Hz. Theoretical predictions agree well with the experimental data. The HMRs may replace HRs in duct noise reduction applications in that at a single operation frequency they have stronger strength to cover a much larger cross section area than that of HRs with similar cavity volume, and they can be designed to provide multiple frequency absorption band.

physics.class-ph↗