16168 research outputs found
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Optimization and experimental investigation of a single-actuation compliant morphing trailing edge for multiple aerodynamic configurations /
No full textThis work presents a low-fidelity optimization method for a compliant morphing wing trailing-edge structure, developed to achieve multiple optimized aerodynamic shapes under combined aerodynamic and control loads using a single actuation pathway. Typically, multiple shape configurations are avoided due to conflicting structural requirements that increase optimization complexity. To address this, a parameterization method based on practical considerations of compliant trailing-edge structures is introduced. A particle swarm optimization algorithm is employed, with multi-objective criteria handled through a penalty-based approach. The algorithm is demonstrated by optimizing the trailing edge for one and two aerodynamic configurations with high accuracy, achieving typical shape deviations of 0.04% and 0.08% relative to the chord for two shapes, and as low as 0.023% for a single shape. Several compliant structures are generated, manufactured, and tested for shape accuracy, including in a wind tunnel to evaluate aerodynamic performance. Experimental investigations confirm the feasibility of achieving two aerodynamic shape configurations with a single structure and show that the proposed methodology can improve the lift-to-drag ratio of a wing section with a deflected compliant trailing edge by more than 12.4% compared to conventional flaps at the same deflection
Development of gas electron multiplier detector system for high-resolution X-Ray imagin /
No full textIn this study, a fully integrated Gas Electron Multiplier (GEM) detector system was employed for high-resolution X-ray imaging. The detector is based on a triple-GEM foil configuration, each with an active area of 10×10cm², housed within a sealed gas chamber. The GEM foils are fabricated from copper foil, featuring a dense array of microscopic holes that enable avalanche multiplication of electrons under high voltage. The triple-GEM cascade ensures high gain, low ion feedback, and excellent spatial resolution. The detector includes a Kapton window, a drift cathode that establishes a uniform electric field across the drift region, guiding primary ionization electrons toward the GEM stack. The multiplied electrons are collected on a 2D readout plate with 256 channels (128 in X and 128 in Y), enabling precise spatial localization of the incident radiation. The readout system is a custom-designed 256-channel board developed by Techtra, interfacing with the GEM detector via four Panasonic® connectors. It integrates four Texas Instruments® DDC264 analog-to-digital converters (ADCs), each offering 64 channels with 20-bit resolution and current-input capability. The detector operates with an Ar/CO₂ (70/30) gas mixture and is powered by a high-voltage supply unit (Caen DT5470N USB HV PS), capable of delivering up to −5kV at 200μA. High-voltage is supplied to the GEM foils via a dedicated HV connector and cable. Gas flow is regulated using a Micromite 1656M4YA dosing valve with micrometric control. The system is housed with dedicated connectors for inputs and outputs, ensuring stable and low-noise operation. To demonstrate the imaging capabilities of the GEM detector, a COOL-X miniature X-ray generator was used. Random objects were placed on the Kapton entrance window and irradiated with X-rays. The COOL-X uses a pyroelectric crystal to generate electrons, which then produce X-rays upon striking a copper target, with peak output reaching approximately 10⁸ photons per second and endpoint energies up to 35kV
Digital tools for sustainable renovation of heritage buildings: from HBIM to low-carbon material selection /
No full textThis paper presents a case study on applying digital tools for the sustainable renovation of a cultural heritage building, the Mikas and Kipras Petrauskas House in Kaunas, Lithuania. The study integrates Heritage Building Information Modeling (HBIM), indoor environmental quality (IEQ) monitoring, and life cycle assessment (LCA) to evaluate renovation solutions in alignment with smart and sustainable city goals. A high-accuracy HBIM model was developed using photogrammetry and laser scanning, achieving less than 2% deviation from validated geometric dimensions. The model provided a reliable foundation for analytical workflows and demonstrated how digital capture can reduce time and mitigate reliance on outdated documentation. Indoor climate measurements indicated critical humidity conditions during the cold season, highlighting the need for improved environmental controls to preserve both occupant comfort and material preservation. LCA was employed to assess the embodied carbon of renovation materials, and alternative selections led to a 22% reduction in CO2e emissions. The results confirm that integrating HBIM, IAQ analysis, and LCA provides a robust methodology for data-driven decision-making in heritage renovation. The approach also supports the future development of digital twin frameworks that balance environmental sustainability with cultural value
Hydrogel-based finger foods: enhancing nutritional intake and swallowing safety in older persons with dysphagia /
No full textBACKGROUND: Dysphagia is a common problem in older adults, characterized as a swallowing disorder that prevents food from passing from the mouth to the esophagus. Besides impairing dietary intake and leading to malnutrition, dysphagia also severely restricts water intake. PURPOSE: This study aimed to develop polysaccharide-based hydrogels as dysphagia-friendly finger foods designed to provide high water content and enable controlled vitamin delivery to older persons with dysphagia. PROCEDURES: Agar-carboxymethylcellulose (Agar-CMC) composite hydrogels with incorporated vitamins C, B9, B, and D3 were developed and tested for their textural and rheological properties, vitamin stability during storage, and vitamin release under simulated gastrointestinal conditions. Finally, a fiberoptic endoscopic swallowing assessment and sensory evaluation were conducted. MAIN FINDINGS: Increasing the agar concentration in Agar-CMC hydrogels improved their internal structure and handling properties as finger foods, while still being easily breakable during swallowing. Agar-CMC hydrogels' structure protected vitamins during processing and six weeks of storage. Vitamin release started immediately and remained steady in the gastric phase, with a noticeable increase at the beginning of the intestinal phase, resulting in 70-100% vitamin release by the end of this phase. The Fiberoptic Endoscopic Swallowing Evaluation confirmed their suitability for individuals with mild to moderate oropharyngeal dysphagia, with a low risk of aspiration (1 point on the Penetration-Aspiration Scale out of 8). PRINCIPAL CONCLUSIONS: The developed Agar-CMC hydrogels present a promising dysphagia-friendly finger food alternative with high water content. They effectively deliver essential vitamins throughout the gastrointestinal tract, and notably demonstrate a low aspiration risk, making them suitable for individuals with mild to moderate oropharyngeal dysphagia
Novel consumer power event-driven methods for remote estimation of smart meter error /
No full textRemote in-service detection of energy metering anomalies and identification of faulty meters remains an active challenge due to the limitations of existing methods. Traditional energy conservation-based techniques require readings from all consumers’ meters and are not applicable in the case of partial deployment of smart meters in the distribution grid. This paper presents two novel methods for remote estimation of active power measurement error of individual smart energy meter that utilizes consumer-side power events. The first approach, Inverse Problem Solution (IPS), utilizes feedforward neural network model trained under reference conditions for the prediction of the expected power change at the location of the sum meter. The power measurement gain error of the consumer meter is estimated by minimizing the difference between the predicted power change and the power change measured by the sum meter. The second approach, Electrical Data Augmentation (EDA), utilizes feature engineering with injection of different levels of gain error of meter power measurement to create dataset for the training of a random forest regression model dedicated to predict the gain error directly. Both techniques were examined using synthetic datasets generated from power flow simulation of low-voltage distribution grid. It is shown that both methods achieve sub-1% root mean square error (RMSE) of estimation of power measurement gain error, with EDA demonstrating slightly superior performance in terms of meter error prediction RMSE and robustness to grid technical losses variations
The effect of external environment factors and founders’ characteristics on digital platform start-up performance. Dynamic competition perspectiveive /
No full textDigital platform start-ups rely on technological innovations to compete with other start-ups and incumbents. Competition by innovation, so-called dynamic competition, radically changes how start-ups leverage the external environment and founders’ characteristics to create superior performance. Although scholars unveiled the significant role of dynamic competition in entrepreneurial ecosystems, it is little known about how external environment factors and founders' characteristics interact under dynamic competition. This study focuses on the healthcare industry, which is a highly innovative sector where digital platform start-ups face unique challenges and opportunities. Using a sample of 235 digital platform start-ups, this study quantifies the impact of external environment factors and analyses the role of founders’ characteristics through managerial effectiveness. The findings reveal that economic freedom and governance quality may negatively affect performance, while founder characteristics enhance managerial effectiveness and significantly support start-up success. This study contributes to the literature by linking digital entrepreneurship with dynamic competition and offers insights into how start-ups can strategically navigate competitive environments to achieve superior performance
Air-coupled ultrasound transduction improvement using vertical piezoelements’ array /
No full textNovel transducer construction is proposed: array of PVDF film strips placed parallel to each other with air gaps between. Films are oriented in such way that strip extension (31 mode) is aligned with emission direction. Transduction is improved by providing better acoustic impedance match to air and increased displacement of emitting surface. Two distinct operation modes are presented: i) emission from the gaps ii) emission from membrane attached to the edges at array top with lower edges backed. In gap emission mode, the transduction efficiency is increased because of two mechanisms. The pressure produced by the expansion of the individual films is concentrated into narrow gap. Also, emission of edges due to height extension. Height extension (31 mode) is much higher than thickness expansion (33 mode) if film height is larger than film thickness. Low, 500 Rayl, equivalent acoustic impedance of gap emission is achieved at film thickness 10 μm and gap with 50 μm. In membrane emission mode, only extension (31 mode) is used, pressure emitted is increased due to large membrane displacement and better match to air. Equivalent acoustic impedance is 500 kRayl at PVDF film thickness 40 μm and 200 μm air gap. Displacement is maximized if PVDF film with large transverse piezoelectric coefficient d31 is used. Experimental measurements are presented. Transmission sensitivity peak for gap emission was 155 mPa/V, for membrane emission mode it was 320 mPa/V. Impressive, more than 270 % fractional bandwidth was confirmed experimentally
Solvent-free manufacturing and 3D printing of ceramic-rich biopolymeric PHA-based piezocomposite for eco-friendly mechanical sensors /
No full textSimilarly to the developments in green electronics, the emerging field of additive piezo-electronics increasingly focuses on more sustainable electroactive materials and cleaner production workflows. However, solution processing with hazardous solvents remains common, even for hybrid organic-inorganic piezoelectric materials (piezocomposites) made from eco-friendly biopolyesters polyhydroxyalkanoates, including ductile copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)(PHBHHx). Therefore, we investigated the solvent-free extrusion-based manufacturing and fused filament fabrication (FFF) of lead-free piezoceramic-rich PHBHHx composite with 80 wt% of barium titanate (BTO). Physicochemical characterization of filaments and prints revealed favorable melt reprocessing capability of PHBHHx as both neat and BTO-rich biopolymers retained chemical structure and thermal stability after three remelting cycles (single or double extrusion at 130 °C–140 °C and FFF at 170 °C). The re-extrusion and FFF processes were calibrated to ensure consistent printability of well-homogenized and well-fused piezocomposite (0–3 connectivity). The tensile loading of neat and BTO-rich PHBHHx structures at increasing speeds revealed complex material behavior of strain-rate-dependent strengthening, weakening, hardening and softening. Despite the high BTO fraction, the composite maintained acceptable flexibility, although the tensile strength decreased due to weaker filler-matrix interfacial bonding. The piezoelectric response and stabilization (d33 decay due to initial ferroelectric depolarization) were analyzed over a wide range of poling fields and durations. The 3D-printed piezocomposite demonstrated excellent high-field poling capability up to ∼22 kV/mm. It provided a comparatively high maximum piezoresponse of ∼11 pC/N, matching the predictions of the Jayasundere–Smith model for two-phase particulate composites. The presented sustainable and scalable melt-based workflow is accessible to the 3D printing community, supporting democratization and further advances in the material extrusion additive manufacturing of piezoelectric sensors, energy harvesters/nanogenerators and other devices. The experimental findings are useful for the development of environmentally safe melt processing routes to produce highly filled PHBHHx-based composites
Framework for the structural analysis of fractional differential equations via optimized model reduction /
No full textFractional differential equations (FDEs) provide a powerful tool for modeling systems with memory and non-local effects, but understanding their underlying structure remains a significant challenge. While numerous numerical and semi-analytical methods exist to find solutions, new approaches are needed to analyze the intrinsic properties of the FDEs themselves. This paper introduces a novel computational framework for the structural analysis of FDEs involving iterated Caputo derivatives. The methodology is based on a transformation that recasts the original FDE into an equivalent higher-order form, represented as the sum of a closed-form, integer-order component G(y) and a residual fractional power series Ψ(x). This transformed FDE is subsequently reduced to a first-order ordinary differential equation (ODE). The primary novelty of the proposed methodology lies in treating the structure of the integer-order component G(y) not as fixed, but as a parameterizable polynomial whose coefficients can be determined via global optimization. Using particle swarm optimization, the framework identifies an optimal ODE architecture by minimizing a dual objective that balances solution accuracy against a high-fidelity reference and the magnitude of the truncated residual series. The effectiveness of the approach is demonstrated on both a linear FDE and a nonlinear fractional Riccati equation. Results demonstrate that the framework successfully identifies an optimal, low-degree polynomial ODE architecture that is not necessarily identical to the forcing function of the original FDE. This work provides a new tool for analyzing the underlying structure of FDEs and gaining deeper insights into the interplay between local and non-local dynamics in fractional systems
Who pays, who graduates? Funding mechanisms and other drivers of graduation in the European Union /
No full textHigher education (HE) funding mechanisms in the European Union (EU) are undergoing substantial reform, with universities facing increasing pressure to improve performance outcomes under constrained public budgets. This study analyses how the design of HE funding mechanisms—specifically, the logic of resource allocation and the principles of performance evaluation, together with the volume of public investment, macroeconomic conditions, and demographic factors—affect graduation rates in the EU. The study uses panel data from 27 EU Member States for the period 2013–2023 and applies multiple regression models with one- to four-year lags to assess the delayed effects of funding and economic factors. The results showed that a larger share of young people in the population and public expenditure per student are positively and statistically significantly associated with higher graduation rates (p 0.05). The most substantial effect was found after two years, confirming the delayed but weakening impact of funding and macroeconomic factors on study graduation rates. The study extends previous work by integrating an analysis of funding design and time dimensions at the EU level. The results emphasise that it is not so much the amount of funding that is important for higher education outcomes, but instead how it is funded—therefore, targeted, student-oriented investments and long-term policy consistency are necessary to achieve higher graduation rates