Search Results (1,013)

The aim of this study is to provide a preliminary assessment of the feasibility of using a three-arm buoy as a small-scale point-absorber wave energy converter under the moderate hydrodynamic conditions of the Baltic Sea. The analysed concept combines an axisymmetric three-floater geometry with two energy-conversion pathways: an electric generator and a pneumatic energy-storage subsystem based on compressed air. The study defines the geometrical and buoyancy parameters of the structure and applies two complementary modelling levels: a simplified screening-level energy estimate and a first-order heave-response model. The extended analysis includes the influence of effective operational density, added mass, PTO damping, conversion-path efficiency, heave RAO and hydrostatic stability. The baseline screening estimate indicates that the total daily energy output may amount to approximately 0.409 kWh under average wave conditions and approximately 0.920 kWh for higher waves. The first-order heave-response model shows that, for an assumed electrical conversion efficiency of 10%, the daily electrical energy estimate ranges from approximately 0.88 kWh/day for the lightweight configuration to approximately 4.12 kWh/day for the most heavily ballasted analysed case. The RAO analysis indicates that increasing the operational mass shifts the natural period towards longer wave periods, although the system remains outside resonance tuning for the reference wave period of 6 s. The hydrostatic analysis indicates that the three-arm configuration increases the waterplane second moment of area compared with a single circular buoy of the same waterplane area and provides a more directionally balanced stability response. The results should be interpreted as conceptual and parametric estimates rather than experimentally validated wave-to-wire performance. Further work should include BEM/CFD-based hydrodynamic coefficients, irregular-wave modelling, multi-degree-of-freedom dynamics, mooring-system coupling and laboratory validation. Full article

Offshore renewable energy is widely recognised as a critical pathway for decarbonising electricity systems, but the integration of floating offshore wind turbines with wave energy converters remains technically challenging. This paper presents a structured literature review of hybrid wave–wind offshore energy platforms, drawing on 114 reviewed sources published between 2000 and 2026. The review classifies hybrid concepts using a three-axis framework based on floating platform type, wave energy converter (WEC) integration approach, and energy-dominance category. It then compares representative configurations, including point absorbers, oscillating water columns, flap-type devices, and heaving torus concepts, with emphasis on hydrodynamic response, energy contribution, structural complexity, mooring implications, validation status, and optimization suitability. The findings show that no single hybrid configuration can be ranked as universally superior because reported performance depends strongly on platform geometry, WEC scale, site wave climate, modelling assumptions, and validation maturity. Point absorber systems offer modularity and lower integration complexity, oscillating water column (OWC)-based systems provide protected power take-off (PTO) integration and moderate hydrodynamic interaction, flap-type systems can provide stronger motion-control potential but impose higher structural and mooring demands, and spar–torus concepts remain geometrically compatible with spar platforms but are generally wind-dominated. The review further shows that optimization method selection should depend on problem class: gradient-based methods are most suitable for local PTO tuning, evolutionary methods for non-convex multi-objective layout problems, surrogate-based methods for high-cost coupled simulations, and data-driven methods for adaptive control. The paper concludes that future progress requires standardized benchmark models, transparent evidence-level reporting, multi-physics co-optimization, techno-economic assessment, and systematic experimental or field validation before definitive concept ranking or commercial-readiness claims can be made. For decision-makers, industry stakeholders, and policymakers, the framework supports early-stage concept screening, identification of technology-specific risk factors, prioritisation of validation and investment pathways, and alignment of hybrid-platform development with site conditions, infrastructure constraints, and policy objectives. Full article

Additively manufactured cellular architectures frequently exhibit brittle failure under impact due to layer-induced stress concentrations. Through the programming of architectural and material design, specifically combining Fused Deposition Modeling (FDM) lattice topology with hyperelastic polyurea infiltration, this study achieves active control over the macroscopic transition from catastrophic structural fragmentation to stable progressive collapse. To evaluate this, auxetic and honeycomb specimens printed with ABS and glass-fiber-reinforced polyamide (PA-GF) were evaluated in unreinforced and polyurea-infiltrated states under quasi-static compression, three-point bending, and Charpy impact loading. Results show that the compressive response depends primarily on cellular topology; the pure auxetic (A-A) configuration provided the highest stiffness and energy absorption. Polyurea infiltration did not significantly alter elastic stiffness but increased post-yield stability, leading to a 96.6% elastic recovery in PA-GF A-A structures. In flexure, the base polymer governed stiffness, with ABS structures measuring 68% stiffer than PA-GF. Unreinforced ABS achieved 34% higher specific energy absorption (SEA) than PA-GF under compression, with the A-H topology maximizing SEA. Under dynamic impact, PA-GF absorbed an average of 70% more energy than ABS, and the H-A configuration recorded the highest impact resistance. The addition of polyurea shifted the failure mode from brittle fragmentation to stable elastomeric deformation, increasing absorbed impact energy by 52% for ABS and over 30% for PA-GF, preventing catastrophic structural failure. Integrating topological sequencing with elastomeric confinement provides a direct method to control energy dissipation and damage tolerance in 3D-printed cellular composites. Full article

Main engine load varies continuously, whereas onboard carbon capture columns are installed with fixed capacities. For liquefied natural gas (LNG)-fueled ships, this mismatch between design and operation makes off-design robustness, rather than nominal-point performance, the governing sizing criterion. This study developed a variable-load design window for onboard monoethanolamine CO₂ capture and evaluated a dual-loop organic Rankine cycle (ORC) as a secondary thermal integration option. A verified process model was applied to a 5 × 5 design–operating matrix (D50–D90/O50–O90). The mismatch was strongly asymmetric. When operating load did not exceed design load, capture rate remained near 90%; under overload, absorber treated only the design-point-equivalent exhaust-gas flow, causing capture performance to deteriorate rapidly. The mean CO₂ avoided rate increased from 57.4% at D50 to 70.4% at D90, while absorber diameter increased from 3.23 to 4.06 m. D70 emerged as the balanced option for low- to medium-load services, D80 marked the transition before full robustness, and D90 was robustness-oriented for frequent high-load operation. The ORC recovered 104–185 kW net power and supplied 231–410 kW LNG-side heating. Results support capacity selection before ORC application; CO₂ liquefaction and storage, voyage-weighted validation, and shipboard ORC feasibility remain outside the present scope. Full article

Effective diabetes management heavily relies on appropriate insulin administration, which strongly depends on the correct administration strategy. In this sense, insulin administration plays a fundamental role, as its use depends on the patient’s clinical condition and diabetes type. Traditional syringe-based methods require proper training to ensure that insulin is successfully delivered into the subcutaneous tissue, where it can be absorbed and metabolized; however, it is desirable to develop an insulin applicator that does not require training for its appropriate use. Aiming to provide support solutions that help patients to develop a correct administration technique, a biodesign-based methodology, coupled with biomimetic concepts, is employed to design a device that assists the user in creating a stable skin fold and guiding needle orientation during injection without requiring exhaustive training for device usage. A three-step approach is employed for the design, where computational fluid dynamics (CFD) and finite element analysis (FEA) methods are employed to ensure that the device produces a laminar insulin flow and the device strength is tested. It should be pointed out both methods are required since complications produced by sudden flows must be avoided, with CFD allowing assessment of the device mechanical properties in terms of the device strength. Initial functional evaluation indicates that the proposed approach does not require extensive training or complex operational procedures, facilitating its integration into everyday use. The device design is validated from the results obtained for the CFD analysis, as no turbulent flow is produced, whereas the FEA indicates that the geometrical form can handle the stresses produced by the folding generation without generating excessive deformations. Moreover, an infrared thermography analysis is also carried out to find out if the folding force generation is located in the zone of interest, the results of which indicate that the device operates in the desired physical zone. Full article

To improve the energy capture efficiency of wave energy converters (WECs), various control strategies based on adjustable power take-off (PTO) systems have been developed. However, such approaches often impose stringent requirements on PTO structural design and generator performance. To address this issue, this paper proposes a novel variable-stiffness point-absorber wave energy converter (VSPAWEC). In the proposed system, a stiffness regulator (SR) composed of a magnetorheological damper (MRD) and a spring mechanism is introduced as a frequency-tuning device, enabling stiffness compensation of the point absorber within a certain operating range. Based on the SR mechanism, a frequency-tracking resonance control strategy is further developed. Specifically, a sliding mode control algorithm is employed to regulate the MRD in real time, allowing the piston rod to track a reference position signal generated from the known dominant wave frequency. In this way, the spring force applied to the buoy can be adjusted adaptively, so that resonance between the buoy and the incident waves can be achieved. Finally, numerical simulations are conducted to evaluate the variable-stiffness characteristics of the proposed VSPAWEC and to verify the effectiveness of the developed frequency-tracking control strategy. The results demonstrate the feasibility of the proposed concept for resonance tuning and wave energy capture enhancement. Full article

As the power density of office computing clusters rises to 200–250 W per chip, the substantial heat generated during operation not only impairs chip performance and shortens lifespan but also compels heating, ventilation, and air conditioning (HVAC) systems to operate at high loads. This increases energy consumption by 30–40% and causes indoor temperature fluctuations that reduce office workers’ comfort. Targeting centralized thermal management for such clusters, this study proposes a hybrid cooling strategy integrating outdoor natural cold air (as a continuous heat sink) with phase change materials (PCMs, for transient heat peak absorption). Six adjustable heating plates (power range: 50–250 W per unit, simulating 7 nm office chips) mimicked heat dissipation in a six-chip cluster. Latent heat storage (LHS) units served as passive cooling, with fan coils as auxiliary for natural/forced convection. By using PCMs (melting point: 48 °C) to absorb transient peaks and coils to utilize outdoor cold air, the system maintained circulating water at approximately 60 °C (steady-state equilibrium temperature under full-load conditions) and kept chip temperatures below 80 °C (industrial safety threshold). The hybrid system reduced combined pump and fan power to 125 W, achieving 75% energy savings compared to the HVAC system (500 W) and 40% savings compared to using only natural cold air (210 W pump and fan power). Positive pressure in the outdoor unit (increasing coil air velocity by 1.2 m/s relative to natural convection) further improved heat dissipation efficiency by 15%. Finally, this study quantifies the influence of PCM thermal conductivity and filling mass on the system’s temperature control performance through numerical simulations, providing direct evidence for parameter design of LHS units. Full article

Fresh engineering students are often required to absorb a large amount of new information within a short period of time, which can be academically and emotionally challenging. To address this challenge, this study introduces AUMOR, a mobile application designed to enhance university orientation by delivering contextual information at the point of need. It integrates GPS-based localization with QR code triggers to provide real-time, location-specific guidance and interactive content through an augmented reality (AR) interface. It uses GPS functionality to provide real-time location-based services, including information about academic buildings, student services, and recreational facilities. The QR codes on devices and laboratory equipment provide relevant information when scanned. A post-deployment user perception survey was conducted using a paper-based questionnaire involving 128 participants, including both students and faculty members. The results indicate that users perceived the application as helpful in enhancing their spatial awareness, navigation confidence, and ability to locate campus facilities, demonstrating high levels of usability and acceptance. The findings suggest that students perceived AUMOR as helpful for university orientation and suggest potential as a scalable solution. Full article

To achieve label-free, highly sensitive, and rapid quantitative detection of spores of wheat scab pathogens, this study developed a flexible terahertz metamaterial perfect absorber based on a composite unit consisting of dual-U-shaped resonators and a central metal rod. The results showed that the metamaterial exhibited near-perfect absorption at two frequencies, 0.53 THz and 2.30 THz, with absorption rates of 99.2% and 99.5%, respectively. A sharp phase shift occurred at the resonance points, enabling significant amplification of weak sensing signals. The refractive index sensitivity was 110 GHz/RIU at low frequencies and 440 GHz/RIU at high frequencies, indicating superior sensing performance in high-frequency modes. Gradient concentration measurements of Fusarium graminearum conidia revealed a good linear relationship between spore concentration and resonance frequency shift (R² = 0.996). The detection limit was 10 spores/μL, with a detection range covering 0–1000 spores/μL. This approach meets the needs for early detection of trace amounts of pathogens and quantitative analysis throughout the disease cycle. As this technique requires no labeling, is non-invasive, and operates rapidly, it provides an efficient new method for real-time monitoring and intelligent control of wheat scab in fields. It also holds great potential for applying terahertz metamaterials in agricultural biosafety applications. Full article

Background: Irinotecan hydrochloride (CPT-11) is an important anticancer drug used in a wide range of regimens to treat colorectal and gastric cancers, and one of its severe side effects is delayed diarrhea. Therefore, based on known circadian variations in intestinal function and drug metabolism, we investigated whether CPT-11-induced delayed diarrhea may be attenuated by the time of dosing. Methods: When CPT-11 was administered to rats at 9:00 or 21:00, CPT-11-induced delayed diarrhea was assessed, and concentrations of CPT-11, its active metabolite SN-38, and SN-38 glucuronide (SN-38GL) in blood, intestinal tissues, and intestinal contents were measured. Results: The severity of diarrhea was significantly less in the 21:00 dosing group compared with the 9:00 dosing group. Blood SN-38 concentrations 8 h after the administration of CPT-11 were significantly higher in the 9:00 dosing group than in the 21:00 dosing group. SN-38, which exerts potent cytotoxic effects, circulates enterohepatically. When SN-38 is absorbed from the intestinal mucosa, intestinal tissues may be injured, resulting in delayed diarrhea. CPT-11 and SN-38 concentrations in intestinal tissues and contents 8 h after the administration of CPT-11 were significantly higher in the 9:00 dosing group than in the 21:00 dosing group at all measurement points. This was consistent with more severe CPT-11-induced delayed diarrhea in the 9:00 dosing group. Conclusions: Chronotherapy with CPT-11 may reduce CPT-11-induced delayed diarrhea. These differences in SN-38 concentrations in the intestinal tract at different dosing times may contribute to the time-dependent reduction in CPT-11-induced delayed diarrhea. Full article

Water security in rapidly urbanising river basins is increasingly threatened by untreated city effluents, industrial discharges, and legacy agricultural contamination. The Tula River basin in central Mexico illustrates this issue, absorbing the majority of Mexico City’s effluent while sustaining a heavily exploited aquifer beneath one of the nation’s largest irrigation districts. This study provides an integrated assessment of surface water and groundwater quality throughout the basin, including the Endhó Dam and its associated aquifer. Water quality analysis revealed severe surface water contamination (WQI > 300), driven by untreated sewage and inadequate sanitation infrastructure. Elevated COD, BOD, and nutrient concentrations indicate significant organic loading and eutrophication risk. Near Tula City, arsenic, copper, and zinc were detected at levels posing direct risks to human health. Groundwater quality was comparatively favourable, with 71% of wells recording WQI < 100; however, arsenic exceeded permissible limits more than twentyfold in select wells, attributed to geological sources. The detection of SVOCs in both hydrological compartments confirms cross-compartment contamination. Point-source reduction alone is insufficient for aquifer recovery; comprehensive sanitation strategies and long-term monitoring are urgently required. These findings carry direct relevance for water governance in megacity-dependent basins globally, where urban, agricultural, and geological stressors demand integrated management approaches. Full article

To investigate the mechanism by which metal bellows affects the dynamic behavior of the mechanical seal system under high pressure and strong vibration conditions in the turbopump, a multi-degree-of-freedom finite element dynamic model is established based on ANSYS Workbench (2024 R2), using a stator-welded metal bellows as the sealing assembly system. The effects of sealing medium pressure and installation offset angle on the dynamic natural characteristics of the bellows assembly are considered. Furthermore, the influence of different operating parameters under radial and axial excitation on the dynamic response of stationary ring and bellows, as well as the amplitude–frequency characteristics of the bellows assembly, are investigated using the base-excitation method. The results indicate that the first three natural frequencies dominate the dynamic response of the assembly and are prone to resonance within the operating frequency range of turbopumps. Radial excitation induces significant high-frequency vibration of the stationary ring, with radial amplitudes exceeding 110 μm, while axial vibration is primarily absorbed by the bellows. Increasing the sealing medium pressure effectively enhances structural stiffness and reduces resonance amplitude, whereas installation misalignment leads to additional resonance points and deteriorates dynamic stability. These findings provide useful guidance for avoiding resonance, improving vibration stability, and optimizing the structural design of mechanical seal bellows assemblies in high-parameter engineering applications. Full article

National risks constitute an important but still underexplored dimension of sustainable development, particularly in countries exposed to institutional fragility, demographic decline, and geopolitical uncertainty. This study identifies and prioritizes the ten most significant risks facing Bulgaria’s development over the next decade, with particular attention to their fiscal and macro-financial transmission channels. The analysis is based on a structured expert survey conducted among 82 specialists from academia, business, research institutions, civil society, and public practice. Respondents assessed 32 potential risks according to likelihood and impact using a five-point scale. A combined priority index was constructed as the product of mean likelihood and mean impact scores. The results show that the most significant risks are concentrated around institutional and systemic vulnerabilities, especially distrust in the rule of law, ineffective healthcare, disinformation, corruption, crisis of statehood, demographic decline, and deterioration in education and infrastructure. The findings indicate that these risks affect Bulgaria’s long-term development through five main fiscal and macro-financial channels: higher sovereign risk premia, expenditure pressure, weaker revenue capacity and investment efficiency, labor market deterioration, and broader financial fragility. The study contributes to the literature on sustainability governance, sovereign resilience, and fiscal sustainability by showing that national resilience depends not only on the management of external shocks, but also on the institutional capacity of the state to absorb long-term structural pressures. The practical applicability of the study lies in the possibility and necessity of conducting a content analysis of the main strategic documents for the country’s development in order to establish the extent to which the identified main risks are reflected in them, as conclusions about the situation and as countermeasure policies. Full article

Background/Objectives: Topical hemostatic biomaterials are used to control diffuse parenchymal bleeding during hepatectomy. TachoSil is a widely used standard fibrin sealant patch. We evaluated the efficacy and safety of InnoSEAL Plus DL, a novel bioinspired absorbable chitosan–catechol/gelatin hemostatic patch, compared with TachoSil. Methods: This multicenter, randomized, single-blind, active-controlled, parallel-group noninferiority trial enrolled adults undergoing hepatectomy who had persistent oozing from the hepatic transection surface despite primary hemostasis. Participants were randomized in a 1:1 ratio to receive InnoSEAL Plus DL or TachoSil. The primary endpoint was hemostatic success within 3 min of application, with a prespecified noninferiority margin of −19.4 percentage points (pp). Safety was assessed up to 30 days postoperatively. Results: Ninety patients were randomized (45 per group). In the per-protocol population, 3 min hemostatic success was achieved in 100.0% of both the InnoSEAL Plus DL (43/43) and TachoSil (41/41) groups. The risk difference was 0.0 pp, and the lower bound of the one-sided 97.5% confidence interval was −8.2 pp, confirming noninferiority. The mean time to hemostasis was similar between groups (1.2 vs. 1.3 min), and no intraoperative rebleeding occurred. Adverse events were reported in 78/90 patients (86.7%) and serious adverse events in 6/90 (6.7%); the latter were typical post-hepatectomy events unrelated to the study devices. No deaths were reported. Conclusions: InnoSEAL Plus DL was noninferior to TachoSil for achieving rapid intraoperative hemostasis during hepatectomy, with no unexpected safety concerns. This bioinspired hemostatic patch is an effective alternative to fibrin sealant, without the use of human-derived proteins. Full article

Meeting the growing demand for renewable energy production requires tapping into a variety of natural resources. Wave energy, while abundant, remains a challenging and often non-economic field. To address this, the present paper proposes and examines an innovative concept for a wave energy converter (WEC). Alongside survivability capabilities, the novel device enables simultaneous extraction of wave energy in two degrees of freedom and, with additional tuning for a range of sea states, achieves higher efficiency compared to existing technologies. As it does not require a link to the seabed or a wharf for production, the concept is suitable for deep water, hence offering higher potential relative to nearshore WECs. In this study, we present the proposed concept and its engineering simplicity, together with mathematical analysis and preliminary results that evaluate the device’s performance under regular and irregular sea conditions. Full article