Search Results (107)

This study examines the landing performance of a four-legged lunar lander equipped with magnetorheological dampers when landing on discrete lunar soil. To capture the complex interaction between the lander and the soil, a coupled dynamic model is developed that integrates flexible multibody dynamics (FMBD), granular material modeling, and a semi-active fuzzy control strategy. The flexible structures of the lander are described using the floating frame of reference, while the lunar soil behavior is simulated using the discrete element method (DEM). A fuzzy controller is designed to achieve the adaptive MR damping force under varying landing conditions. The FMBD and DEM modules are coupled through a serial staggered approach to ensure stable and accurate data exchange between the two systems. The proposed model is validated through a lander impact experiment, demonstrating good agreement with experimental results. Based on the validated model, the influence of discrete lunar regolith properties on MR damping performance is analyzed. The results show that the MR-based landing leg system can effectively absorb impact energy and adapt well to the uneven, granular lunar surface. Full article

Background/Objectives: Increasing the bioavailability of poorly absorbed drugs is a continuous challenge in modern pharmaceutical technology. This is due to the problematic nature of BCS class IV active pharmaceutical ingredients: these drugs possess poor solubility and membrane permeability. Moreover, many undergo immediate efflux and/or rapid systemic metabolism after absorption. This project aimed to improve the bioavailability of BCS class IV drugs by formulating gastroretentive self-emulsifying systems using curcumin as a model drug. Methods: The base of the systems was created by melting emulsifying agents, dissolution retardants, and PEGs together. Curcumin was added after the mixture was cooled slightly. Aqueous dispersions of several compositions were characterized by dynamic light scattering. After screening these results, the viscosities of the selected formulations were evaluated. Dissolution retardants were selected and added to the most superior samples, and their dissolution profiles were compared. Gastroretention of the final formulation was achieved by dispersing air in the molten system through melt foaming; internal structure was assessed by microCT, and physicochemical properties by PXRD and DSC. Cytotoxicity was measured in Caco-2 cells using MTT and Neutral Red assays, and transcellular transport was also studied. Results: Based on these results, a homogeneous gastric floating system was developed. We observed an advantageous cytotoxic profile and increased bioavailability. Conclusions: Overall, we were able to create a self-emulsifying gastroretentive formulation displaying extended release and gastric retention with a low amount of cost-efficient excipients. Full article

An innovative multi-absorber 1 MW wave energy converter (WEC), Nankun, is proposed for efficient wave energy extraction. It comprises a semi-submersible floating platform, a wave energy capture mechanism, a hydraulic energy conversion system, and a mooring system. The WEC operates by converting fluctuating wave power into stable electrical output through a unique sharp eagle-shaped wave absorber coupled with a hydraulic energy conversion module. Scaled model experiments (1:25) demonstrated energy-capture efficiency ranges predominantly between 30% and 50% across 0.8–1.4 s wave periods, with a peak of 56.17%. Analysis of the wave direction effect revealed that the device achieved significantly a higher energy capture at 180 deg compared with 0 deg wave headings, with a relative efficiency ratio of approximately 1.0:0.6~0.8. A full-scale prototype with 10 absorbers was deployed in the South China Sea, achieving grid connection in November 2023. Operational data confirmed viability and generation capacity, with the peak daily output reaching 9850 kWh and a cumulative production of 89,852 kWh over 20 days. Full article

The integer precise point positioning (IPPP) technique significantly improves the accuracy of positioning and time and frequency transfer by restoring the integer nature of carrier-phase ambiguities. However, in practical applications, IPPP performance is often degraded by day-boundary discontinuities and instances of incorrect ambiguity resolution, which can compromise the reliability of time transfer. To address these challenges and enable continuous, robust, and stable IPPP time transfer, this study proposes an effective approach that utilizes narrow-lane ambiguities to absorb receiver clock jumps, combined with a robust sliding-window weighting strategy that fully exploits multi-epoch information. This method effectively mitigates day-boundary discontinuities and employs adaptive thresholding to enhance error detection and mitigate the impact of incorrect ambiguity resolution. Experimental results show that at an averaging time of 76,800 s, the frequency stabilities of GPS, Galileo, and BDS IPPP reach 4.838 × 10⁻¹⁶, 4.707 × 10⁻¹⁶, and 5.403 × 10⁻¹⁶, respectively. In the simulation scenario, the carrier-phase residual under the IGIII scheme is 6.7 cm, whereas the robust sliding-window weighting method yields a lower residual of 5.2 cm, demonstrating improved performance. In the zero-baseline time link, GPS IPPP achieves stability at the 10⁻¹⁷ level. Compared to optical fiber time transfer, the GPS IPPP solution demonstrates superior long-term performance in differential analysis. For both short- and long-baseline links, IPPP consistently outperforms the PPP float solution and IGS final products. Specifically, at an averaging time of 307,200 s, IPPP improves average frequency stability by approximately 29.3% over PPP and 32.6% over the IGS final products. Full article

To achieve the ‘zero carbon’ target, offshore renewable energy exploration plays a key role in many countries. Offshore wind energy and wave energy are both important offshore renewable energies. With the target to reduce the cost of energy, a new combined wind and wave energy converter is proposed in this work. The new concept consists of a spar-type floating wind turbine and a multi-section pitch-type wave energy converter (WEC). The WEC is attached to the spar column and consists of multiple sections with different lengths to absorb wave energy at different wave frequencies, i.e., multi-band absorption. Through multi-band wave energy absorption, the total power is expected to increase. In addition, through synergetic design, the dynamic motions of the platform are expected to decrease. In this paper, a fully coupled numerical model of the concept is established, based on the hybrid time–frequency-domain simulation framework. The frequency-domain hydrodynamic properties were transferred to the time domain. Then, the dynamic performance of the combined concept under wind–wave conditions was studied, especially under operational conditions. Mechanical couplings among multiple floating bodies were taken into account. To demonstrate the WEC effects on the floating wind turbine, the dynamic performance of the combined wind–wave energy converter concept was compared with the segregated floating wind turbine, with a focus on motions and output power. It was expected that the average overall output power of the multi-section WEC could be above 160 kW. The advantages of the combined concept are demonstrated. Full article

The constant increase in industrialization and urbanization has led to the regular discharge of wastewater into the environment in excessive amounts, which has caused significant impacts on both human and wildlife ecosystems. The sustainable management and treatment of wastewater, whether of industrial or domestic origin, represents a crucial challenge in this century. In this study, phytoremediation was employed as a wastewater treatment strategy using two species of aquatic macrophytes: water hyacinth (Eichhornia crassipes) and duckweed (Lemna minor). The study was conducted over seven consecutive evaluation periods, with five-day intervals between each. The objective was to apply the multivariate HJ-Biplot methodology to evaluate the effects of phytoremediation of two species of aquatic microphytes on the physicochemical characteristics of wastewater from Milagro canton, Ecuador. Additionally, a microbiological analysis was conducted to determine the effectiveness of the floating macrophytes. The analysis was based on the measurement of various physicochemical parameters, such as pH, electrical conductivity (EC), dissolved oxygen (DO), oxidation–reduction potential (ORP), salinity, total dissolved solids (TDSs), biochemical oxygen demand (BOD), chemical oxygen demand (COD), hardness, and temperature. The results showed that the highest efficiency in pollutant removal was achieved with duckweed (Lemna minor) in five out of nine measured parameters, suggesting that this species was the most effective compared to the control sample and Eichhornia crassipes. The capacity of these macrophytes for wastewater treatment was confirmed by this study. To ensure effective water purification, timely extraction of aquatic macrophytes from water bodies is recommended. If this collection is not properly carried out, the nutrients absorbed and stored in the plant tissues may be released back into the aquatic environment due to plant decomposition. Full article

This paper presents a numerical study on the structural vibrations of a TLP-supported NREL 5MW wind turbine equipped with a tuned vibration absorber (TVA) in the nacelle. The analysis was focused on tower bending deflections and was conducted using a reference OpenFAST V3.5.3 dedicated wind turbine modelling software and a finite element simulation framework based on Comsol Multiphysics V6.3 which was newly developed for this study. The obtained four-degree-of-freedom (4-DOF) tower bending model was transferred using modal decomposition to the MATLAB/Simulink R2020b environment, where a 2-DOF TLP surge/sway model and a bidirectional (2-DOF) TVA model were embedded. The wind field was approximated by a Weibull distribution of velocities (8.86 m/s mean, 4.63 m/s standard deviation). It was combined with the wave actions simulated using a Bretschneider spectrum with a significant height of 2.5 m and a peak period of 8.1 s. The TVA model used was either the standard NREL reference 20-ton passive TVA, a 10-ton passive, or a 10-ton controlled TVA (the latter two tuned to the tower’s first bending mode). The controlled TVA utilised a magnetorheological (MR) damper, either operating independently (forming a semi-active MR-TVA) or simultaneously with a force actuator, forming, in this case, a hybrid H-MR-TVA. Both aligned and 45°/90° misaligned wind–wave excitations were examined to investigate the performance of a 10-ton real-time controlled (H-)MR-TVA operating with less working space. In aligned conditions, the semi-active and hybrid MR-TVA solutions demonstrated superior tower vibration mitigation, reducing maximum tower deflections by 11.2% compared to the reference TVA and by 14.9% with regard to the structure without TVA. The reduction in root-mean-square deflection reached up to 4.2%/2.9%, respectively, for the critical along-the-waves direction, while the TVA stroke reduction reached 18.6%. For misaligned excitations, the tower deflection was reduced by 4.3%/4.8% concerning the reference 20-ton TVA, while the stroke was reduced by 22.2%/34.4% (for 45°/90° misalignment, respectively). It is concluded that the implementation of the 10-ton real-time controlled (H-)MR-TVA is a promising alternative to the reference 20-ton passive TVA regarding tower deflection minimisation and TVA stroke reduction for the critical along-the-waves direction. The current research results may be used to design a full-scale semi-active or hybrid TVA system serving a TLP-supported floating offshore wind turbine structure. Full article

Because of its reliability, large reserves, and high safety standards, wave energy power generation has become an important part of the renewable energy industry. Hybrid-sized wave energy converter arrays consist of floats of different sizes. They have higher output power and stability and are the future development direction of wave power generation. However, the energy-absorbing floats in existing power calculation models are still in a traditional uniform-size configuration and cannot accurately calculate the energy generated by hybrid-sized wave energy converter arrays. In this paper, a time-domain power calculation model of hybrid-sized wave energy converter arrays is proposed. Based on linear wave theory, a frequency-domain hydrodynamic model is constructed and transformed into a time-domain model. The time-domain characteristics and influencing factors of wave energy converters are analyzed. Finally, a time-domain power calculation model of hybrid-sized wave energy converter arrays is established. Based on the irregular model setting and water entry conditions, an experimental verification study on the power calculation model is carried out using the wave energy converter previously developed by the research team. The results show that the average error of the power calculation model proposed in this paper is less than 10%, demonstrating the accuracy of the model. Full article

Wave energy is an increasingly attractive renewable energy source due to its potential and predictability. Various Wave Energy Converters (WECs) have been developed, including attenuators, overtopping devices, and point absorbers. The Wave Dragon, an overtopping device, is a floating structure anchored to the seabed with a mooring system. It uses two reflectors to guide incoming waves into a central reservoir, where the captured water flows through turbines to generate electricity. This study enhances the realism of Wave Dragon simulations by modeling it as a moving structure with moorings, addressing key gaps in prior research. Real-time wave data from the Caspian Sea, collected over a year, were used to develop a 3D model and analyze the device’s performance under varying wave conditions. Four significant wave heights (Hs) of 1.5, 2.5, 3.5, and 4.5 m were tested. The results demonstrate that higher wave heights increase water flow through the turbines, leading to higher energy output, with monthly energy generation recorded as 16.03, 25.95, 31.45, and 56.5 MWh for the respective wave heights. The analysis also revealed that higher wave heights significantly increase pressure forces on the Wave Dragon, from 2.97 × 10⁵ N at 1.5 m to 1.95 × 10⁶ N at 4.5 m, representing a 6.5-fold increase. These findings underscore the potential of Wave Dragons to enhance renewable energy production while ensuring structural robustness in varying wave conditions. Full article

This research paper explores an approach to enhancing the economic viability of the heaving wave energy converters (WECs) of both cylinder-shaped and torus-shaped devices, by integrating them with four established, floating offshore wind turbines (FOWTs). Specifically, the approach focused on the wave power performance matrix. This integration of WECs and FOWTs not only offers the potential for shared construction and maintenance costs but also presents synergistic advantages in terms of power generation and platform stability. The study began by conducting a comprehensive review of the current State-of-the-Art in co-locating different types of WECs with various foundation platforms for FOWTs, taking into consideration the semi-submersible, spar and barge platforms commonly employed in the offshore wind industry. The research took a unified approach to investigate more and new WEC arrays, totaling 20 configurations across four distinct FOWTs. The scope of this study’s assumption primarily focused on the hydrodynamic wave power performance matrix, without the inclusion of aerodynamic loads. It then compared their outcomes to determine which array demonstrated superior wave energy under the key metrics of total absorbed power, capture width, and interaction factor. Additionally, the investigation could serve to reinforce the ongoing research and development efforts in the allocation of renewable energy resources. Full article

Wave energy converters (WECs) integrated into breakwaters present a promising solution for combining coastal protection with renewable energy generation, addressing both energy demands and environmental concerns. Additionally, this integration offers cost-sharing opportunities, making the overall investment more economically viable. This study explores the potential of a hinged point-absorber WEC, specifically designed as a floating hinged half-sphere, by assessing the device’s power output and comparing two different breakwater configurations. To evaluate the device’s performance, a comprehensive numerical and experimental approach was adopted. Numerical simulations were carried out using a radiation-diffraction model, a time domain tool for analyzing wave–structure interactions. These simulations predicted average power outputs of 25 kW for sloped breakwaters and 18 kW for vertical breakwaters located at two strategic sites: the Port of Leixões and the mouth of the Douro River in Portugal. To validate these predictions, a 1:14 scale model of the WEC was constructed and subjected to testing in a wave–current flume, replicating different sea-state conditions. The experimental results closely aligned with the numerical simulations, demonstrating a good match in terms of relative error and relative amplitude operator (RAO). This alignment confirms the reliability of the predictive model. These findings support the potential of integrating WECs into breakwaters, contributing to port energy self-sufficiency and decarbonization. Full article

Salvinia auriculata Aublet is a floating aquatic plant, capable of absorbing the excess of nutrients and water contaminants and can be used in effluent treatment plants. The ability to survive in degraded areas may be related to the association with beneficial bacteria capable of promoting plant growth. However, little is known about the microbiota associated with this aquatic plant and its potential application to the aquatic environment. In this sense, this work aims to identify bacteria associated with S. auriculata that could be able to promote plant growth. Eighteen bacterial strains were identified by sequencing of the 16S rRNA gene, belonging to the genera Agrobacterium, Bacillus, Curtobacterium, Enterobacter, Pseudomonas, Siccibacter, and Stenotrophomonas. All isolates produced indole compounds, 12 fixed N₂, and 16 solubilized phosphate. A new strain of Enterobacter (sp 3.1.3.0.X.18) was selected for inoculation into S. auriculata. For this purpose, 500 mL of nutrient solution and 1 g of the plant were used in the control and inoculated conditions. Enterobacter inoculation promoted a significant increase (p ≤ 0.05) in fresh plant biomass (17%) after 4 days of cultivation. In summary, the present study characterized 18 plant-growth-promoting bacteria isolated from S. auriculata with potential for biotechnological application, such as the production of bioinoculants or biomass resources, to protect or improve plant growth under conditions of stress. Full article

Elastic peak electron spectroscopy (EPES) analyzes the line shape of the elastic peak. The reduction in energy of the elastic peak electrons is the result of energy transfer to the target atoms, a phenomenon known as recoil energy. EPES differs from other electron spectroscopies in its unique ability to identify hydrogen in polymers and hydrogenated carbon-based materials. This feature is particularly noteworthy as lighter elements exhibit stronger energy shifts. The energy difference between the positions of the elastic peak of carbon and the elastic peak of hydrogen tends to increase as the kinetic energy of the incident electrons increases. During electron irradiation of an insulating polymer, if the number of secondary electrons emitted from the surface is less than the number of electrons absorbed in the sample, the surface floats energetically until it stabilizes at a potential energy $e{V}_s$. As a result, the interaction energy changes and modifies the energy difference between the elastic peaks of hydrogen and carbon. In this study, the charge effects are evaluated using the Monte Carlo method to simulate the EPES spectra of electrons interacting with polystyrene and polyethylene. Full article

In the early stages of developing wave energy converter (WEC) projects, a quantitative assessment of component failure consequence costs is essential. The WEC types, deployment site features, and accessibility should all be carefully considered. This study introduces an operation and maintenance failure consequence cost (O&M-FC) model, distinct from conventional O&M models. The model is illustrated with case studies at three energetic Atlantic sites, each of which considers two types of generic floating WECs: a 300 kW point absorber (PA) with a hydraulic power-take-off (PTO) and a 1000 kW oscillating water column (OWC) with an air-wells-turbine PTO. This study compares 39 failure modes for PA and 27 for OWC in terms of direct repair costs and indirect lost production costs, examining the impact of location accessibility, capacity factors, and the mean annual energy production. The discussion revolves around the sensitive parameters. Recommendations for failure mitigations are presented, and the impact of planned maintenance (PM) during the operational phase is examined for 20 MW PA and OWC WEC projects. For a given WEC type, the method thoroughly evaluates how the location affects performance metrics. It offers a decision-making tool for determining optimal PM intervals to meet targets such as O&M costs, operating profit, or availability. Full article

This study proposes a novel point absorber wave energy converter (WEC) utilizing an inertial adjusting mechanism for performance evaluation. A conceptual design is introduced to explain the WEC’s functionality. Adjustable masses are incorporated to tune the natural frequency of the power take-off (PTO) system, matching the excitation frequencies of incoming waves. To analyze the system’s behavior, a coupled mechanical and hydrodynamic time domain simulation is presented. This simulation, built primarily in MATLAB/Simulink, focuses on a truncated floating buoy connected to a bidirectional gearbox. Since the WEC operates under various wave conditions, hydrodynamic parameters are determined and simulated in the frequency domain using ANSYS AQWA wave interaction software (version number 2021R1). Finally, a prototype is constructed and tested in a wave tank. Test results under different wave conditions are presented and compared to assess the proposed WEC’s performance. Full article