It is projected that, in the following years, the wind-energy industry will maintain its rapid growth over the last few decades. Such growth in the industry has been accompanied by the desirability and demand for larger wind turbines aimed at harnessing more power. However, the fact that massive turbine blades inherently experience increased fatigue and ultimate loads is no secret, which compromise their structural lifecycle. Accordingly, this demands higher overhaul-and-maintenance (O&M) costs, leading to higher cost of energy (COE). Introduction of flow-control devices on the wind turbine is a plausible solution to this issue. Flow-control mechanisms feature the ability to effectively enhance/suppress turbulence, advance/delay flow transition, and prevent/promote separation, leading to enhancement in aerodynamic and aeroacoustics performance, load alleviation and fluctuation suppression, and eventually wind turbine power augmentation. These flow-control devices are operated primarily under two schemes: passive and active control. Development and optimization of flow-control devices present the potential for reduction in the COE, which is a major challenge against traditional power sources. This review performs a comprehensive and up-to-date literature survey of selected flow-control devices, from their time of development up to the present. It contains a discussion on the current prospects and challenges faced by these devices, along with a comparative analysis centered on their aerodynamic controllability. General considerations and conclusive remarks are presented after the discussion.

A nine degree-of-freedom model of one stage gear system is presented in this research work. The gearbox structure is coupled with the vibration of the gear shaft. The model considers gear size, errors, and faults. The model includes varying meshing stiffness and a realistic representation of the gear transmission error (TE) and gear faults. Gear TE is modeled as a displacement excitation. The model equations are solved using Matlab and using parameters representing a real experimental gearbox rig. Experimental and simulated data are compared for different operating speeds, torque loads, and gear cracks. The simulation results are in good agreement with the experimental ones. The authors believe that the model presented here can be used in studying gear faults and would be very useful in developing gear fault monitoring techniques.

Stimuli-responsive hydrogels are an emerging class of smart materials with immense potential across biomedical engineering, soft robotics, environmental systems, and advanced manufacturing. In this review, we present an in-depth exploration of their material design, classification, fabrication strategies, and real-world applications. We examine how a wide range of external stimuli—such as temperature, pH, moisture, ions, electricity, magnetism, redox conditions, and light—interact with polymer composition and crosslinking chemistry to shape the responsive behavior of hydrogels. Special attention is given to the growing field of 4D printing, where time-dependent shape and property changes enable dynamic, programmable systems. Unlike existing reviews that often treat materials, stimuli, or applications in isolation, this work introduces a multidimensional comparative framework that connects stimulus-response behavior with fabrication techniques and end-use domains. We also highlight key challenges that limit practical deployment—including mechanical fragility, slow actuation, and scale-up difficulties—and outline engineering solutions such as hybrid material design, anisotropic structuring, and multi-stimuli integration. Our aim is to offer a forward-looking perspective that bridges material innovation with functional design, serving as a resource for researchers and engineers working to develop next-generation adaptive systems.

A low-cost, photothermally efficient hydrogel evaporator was fabricated using sodium alginate, poly­(vinyl alcohol), graphite, and multiwalled carbon nanotubes (MWCNTs) via a simple foaming–freezing–ionic cross-linking method. The optimized hydrogel (H2) achieved a high evaporation rate of 3.1 kg/m²·h with a solar-to-vapor efficiency of 89% under 1 sun irradiation. XRD analysis showed a reduced crystallite size (9.7 ± 0.3 nm), which was attributed to the improved pore structure and water transport characteristics. SEM images and porosity measurements revealed an interconnected porous network with 85% porosity, supporting capillary flow. The hydrogel exhibited sustained performance at high salinity (>2.1 kg/m²·h at 20 wt % NaCl), and after 20 brine cycles, its efficiency loss was 99% salt ion rejection using real seawater samples, while compression tests showed a higher compressive stress (0.233 MPa) due to MWCNT reinforcement as compared to that without MWCNTs (0.192 MPa). Statistical t tests confirmed significant performance differences between hydrogel variants. The fabrication cost of the system was estimated to be approximately 5.5 USD/m², notably lower than several existing systems (over 40 USD/m²). These findings underscore the hydrogel’s potential for decentralized solar desalination owing to its strong photothermal response, mechanical durability, self-cleaning capability, and low production cost. Future work will explore large-scale implementation and further pore structure optimization.