Kan Huang

Intermittently operated, tankless reverse osmosis (RO) systems are widely used in decentralized and point-of-use applications, yet water stagnation during idle periods remains a critical challenge, leading to degraded water quality, accelerated fouling, and performance loss. This study presents an experimentally validated engineering solution that eliminates stagnant water in intermittently operated RO systems. A dual-membrane RO configuration with flexible series–parallel switching was developed, enabling membranes to alternate between production and flushing modes. An adaptive control strategy, integrated into the system hardware, regulates membrane switching and flushing based on real-time feed-water quality. The proposed configuration and control framework was evaluated under representative intermittent operating conditions. Experimental results show that the zero-stagnant-water strategy effectively prevents residual water accumulation during shutdown and maintains stable permeate quality, with total dissolved solids consistently below 10 mg/L. Long-term testing further demonstrates reduced membrane fouling and slower performance degradation compared with conventional fixed-operation schemes, resulting in enhanced desalination efficiency and operational stability. Owing to its modular design and simple control logic, the proposed approach is readily transferable to decentralized and point-of-use membrane water treatment systems requiring reliable, high-quality water under intermittent operation.

Given the prejudicial environmental effects of fossil-fuel based energy production, renewable energy sources can contribute significantly to the sustainability of human society. As a clean, cost effective and inexhaustible renewable energy source, wind energy harvesting has found a wide application to replace conventional energy productions. However, concerns have been raised over the noise generated by turbine operating, which is helpful in fault diagnose but primarily identified for its adverse effects on the local ecosystems. Therefore, noise monitoring and separation is essential in wind turbine deployment. Recent developments in condition monitoring provide a solution for turbine noise and vibration analysis. However, the major component, aerodynamic noise is often distorted in modulation, which consequently affects the condition monitoring. This study is conducted to explore a novel approach to extract low-frequency elements from the aerodynamic noise background, and to improve the efficiency of online monitoring. A framework built on the spline envelope method and improved local mean decomposition has been developed for low-frequency noise extraction, and a case study with real near-field noises generated by a mountain-located wind turbine was employed to validate the proposed approach. Results indicate successful extractions with high resolution and efficiency. Findings of this research are also expected to further support the fault diagnosis and the improvement in condition monitoring of turbine systems.

Topological interface states have attracted extensive research interest due to their unprecedented field confinement and enhancement at the interface between two one-dimensional phononic crystals with distinct topological characteristics. However, the realization of the contactless, nondestructive, and intelligent tunability of topological interface states, as the foundation for designing novel devices with unconventional functionalities, still remains a great challenge. Here, we introduce intelligent magnetoelastic materials to the topological system and realize magnetically tunable topological interface states for Lamb waves in one-dimensional phononic crystal slabs composed of alternating nonmagnetic and magnetoelastic layers. The properties of magnetoelastic layers can be tuned with noncontact, nondestruction, and intelligence by an external magnetic field. By changing the value of the external magnetic field applied on intercell and intracell magnetoelastic layers, the spatial variation of the properties of magnetoelastic layers is induced, resulting in an in situ topological phase transition. We demonstrate that topological interface states appear at the interface between two topologically different magnetoelastic phononic crystal slabs. Furthermore, based on the tunability of the external magnetic field, the existence of topological interface states can be switched and the frequency of topological interface states can be continuously tuned. In particular, the arbitrary positions of topological interface states can be dynamically achieved by varying the external magnetic field without altering the structure. Our tunable topological system can enable intelligent Lamb-wave devices with remarkable functionalities, which can lead to significant advances in intelligently controlled Lamb-wave switches, magnetically tunable frequency selectors, and magnetic control Lamb-wave communications.