Search Results (134)

This study evaluated the differential effects of an advanced Vivifrail D-level exercise intervention on arterial stiffness, functional fitness, and body composition in robust older women with varying baseline fitness levels. A total of 41 participants were assigned to a higher-fitness group (HFG, n = 22) or a lower-fitness group (LFG, n = 19) based on their 30 s chair stand performance. Over 12 weeks, both groups completed five weekly sessions incorporating strength, balance, aerobic, and dual-task elements. Significant within-group improvements were observed in the arm curl test (HFG: p = 0.031; LFG: p = 0.002), chair stand (LFG: p < 0.001), and 2 min step test (LFG: p = 0.002). Between-group analysis showed greater percentage gains in the LFG for the chair stand (33.8% ± 28.2% vs. 7.1% ± 21.6%, p = 0.001) and step test (13.7% ± 14.5% vs. 5.3% ± 14.7%, p = 0.040). No significant changes were found in handgrip strength, gait speed, pulse wave velocity, or muscle mass. These results suggest that the modified Vivifrail protocol enhances lower-limb endurance in lower-fitness individuals, but additional adaptations may be necessary to impact vascular and compositional outcomes. Full article

Semi-submerged curtain breakwaters are increasingly favored to protect marinas and other microtidal basins, yet they are still almost exclusively designed with deterministic wave transmission equations. This study introduces a fully probabilistic design framework that translates uncertainty in wave climate and water level design parameters into explicit confidence limits for transmitted wave height. Using Latin Hypercube Sampling, input uncertainty is propagated through a modified Wiegel transmission model, yielding empirical distributions of the transmission coefficients K_t and H_t. Our method uses the associated safety factor required to satisfy a 95% non-exceedance criterion, SF₉₅. Regression analysis reveals the existence of a strong inverse linear relationship (R = −0.9) between deterministic K_t and the probabilistic safety factor, indicating that designs trimmed to low nominal transmission (e.g., K_t ≤ 0.35) must be uprated by up to 55% once parameter uncertainty is acknowledged, whereas concepts with greater transmission require far smaller margins. Sobol indices show that uncertainty in H_m0 and T_p each contribute ≈40% of the variance in H_t for a tide signal standard deviation of σ_η = 0.16 m, while tides only become equally important when σ_η > 0.30 m. Model-based uncertainty is negligible, standing at under 8%. The resulting lookup equations allow designers to convert any deterministic K_t target into a site-specific probabilistic limit with a single step, thereby embedding reliability into routine breakwater sizing and reducing the risk of underdesigned marina and port structures. Full article

The present study analyzes the hydrodynamic performance of an asymmetric offshore Oscillating Water Column device positioned in close proximity to multiple bottom standing and fully submerged breakwaters and trenches. The breakwaters and trenches are located on the leeward side of the Oscillating Water Column device. The structures are investigated in combination with a shore-fixed vertical wall. The analysis is carried out using the Boundary Element Method based on the linear potential flow theory. The results are compared with the existing analytical, numerical, and experiment results available in the literature. The effects of the various shape parameters of the submerged breakwaters/trenches and the shape parameters of the Oscillating Water Column device are investigated. The results show that the resonance effects on the efficiency performance increase as the number of breakwaters/trenches increases. The undulating bottom trench shape is effective in improving the efficiency of the Oscillating Water Column device compared to the breakwater. The efficiency bandwidth is greater in the case of a rectangular trench than in the case of a parabolic- or triangular-shaped trench. In addition, the first peak value in the efficiency curve for a lower frequency is higher in the case of a larger-draft Oscillating Water Column device front wall compared to that of the rear wall. This study demonstrates that in the long wave-length regime, a zero efficiency point is observed between two consecutive resonant peaks, whereas in the intermediate and short wave-length regimes, a trough and a zero efficiency point alternately occur between two consecutive resonance peaks. Various parameters relevant to the behavior of the Oscillating Water Column Wave Energy Converter, such as radiation susceptance, radiation conductance, hydrodynamic efficiency, and volume flux due to a scatter potential, are addressed. Full article

This research explores the underappreciated traditional cold-water baths of Western Anatolia, once integral to the region’s agrarian culture. Due to waves of change, which had markedly begun by the pandemic in 2019 and the aftermath of the 2020 Samos earthquake, there has been a growing interest in living in peri-urban areas, resulting in the invasion of agricultural grounds by new construction, mainly including detached houses with gardens. Such a harsh growth not only threatens the fertile lands, but also the irreplaceable cultural heritage they embrace. In this regional frame, this study focuses on three surviving baths within the Karaburun Peninsula, casting light on their current precarious state as relics of a diminishing rural way of life and local heritage. The traditional cold-water baths, constructed amidst agricultural fields for seasonal use in select villages throughout İzmir, stand as unique exemplars of rural architecture. Characterised by their singular domed chambers and their reliance on water from adjacent wells, these structures today face abandonment and disrepair. Through a multi-disciplinary lens blending ethnography, oral history, and spatial analysis, this paper portrays these unassuming yet culturally impactful baths, elucidating their intrinsic value within the heritage domain. The inquiry contributes significantly to the heritage conservation discussion, highlighting the broad spectrum of values beyond mere historical interest. By articulating the symbiotic relationship between heritage and its community, this research underscores the pressing need to weave these baths into the fabric of current social structures, safeguarding their place within the collective memory. Full article

Impulse ultrawideband (UWB) synthetic aperture radar (SAR) combines high-azimuth-range resolution with robust penetration capabilities, making it ideal for applications such as through-wall detection and subsurface imaging. In such systems, the performance of UWB antennas is critical for transmitting high-power, large-bandwidth impulse signals. However, two primary factors degrade radar imaging quality: (1) inherent limitations in antenna radiation efficiency, which lead to low-frequency signal loss and subsequent time-domain ringing artifacts; (2) impedance mismatch at the antenna terminals, causing standing wave reflections that exacerbate the ringing phenomenon. This study systematically analyzes the mechanisms of ringing generation, including its physical origins and mathematical modeling in SAR systems. Building on this analysis, we propose a Bayesian ringing suppression algorithm based on sparse optimization. The method effectively enhances imaging quality while balancing the trade-off between ringing suppression and image fidelity. Validation through numerical simulations and experimental measurements demonstrates significant suppression of time-domain ringing and improved target clarity. The proposed approach holds critical importance for advancing impulse UWB SAR systems, particularly in scenarios requiring high-resolution imaging. Full article

Background/Objectives: Carotid artery stenosis (CAS) is one of the main causes of stroke, and the vulnerability of plaque has been proved to be a determinant. A joint analysis of shear wave elastography, a radiofrequency echo-based wall tracking technique for arterial stiffness evaluation, and of autonomic and baroreflex function is proposed to noninvasively, preoperatively assess plaque vulnerability in asymptomatic CAS patients scheduled for carotid endarterectomy. Methods: Elastographic markers of arterial stiffness were derived preoperatively in 78 CAS patients (age: 74.2 + 7.7 years, 27 females). Autonomic and baroreflex markers were also assessed by means of an analysis of the beat-to-beat fluctuations in heart period and systolic arterial pressure, derived at rest in supine position (REST) and during active standing. Postoperative analysis identified 36 patients with vulnerable plaque (VULN) and 42 with stable plaque (STABLE). Results: Baroreflex sensitivity (BRS) at a respiratory rate decreased during STAND only in VULN patients, being much higher at REST compared to STABLE levels. Autonomic indexes were not helpful in separating experimental conditions and/or populations. The Young’s modulus (YM) of the plaque was lower in the VULN group than in the STABLE one. Cardiovascular control and elastographic markers were significantly correlated only in VULN patients. A multivariate logistic regression model built combining YM and BRS at the respiratory rate improved the prediction of plaque vulnerability, reporting an area under the ROC curve of 0.694. Conclusions: Noninvasive techniques assessing shear wave elastography and baroreflex control could contribute to the early detection of plaque vulnerability in patients with asymptomatic CAS. Full article

The propagation of interface acoustic waves (IAWs) in 128° YX-LiNbO₃/SU-8/overcoat structures was theoretically studied and experimentally investigated for different types of overcoat materials and thicknesses of the SU-8 adhesive layer. Three-dimensional finite element method analysis was performed using Comsol Multiphysics software to design an optimized multilayer configuration able to achieve an efficient guiding effect of the IAW at the LiNbO₃/overcoat interface. Numerical analysis results showed the following: (i) an overcoat faster than the piezoelectric half-space ensures that the wave propagation is confined mainly close to the surface of the LiNbO₃, although with minimal scattering in the overcoat; (ii) the presence of the SU-8, in addition to performing the essential function of an adhesive layer, can also promote the trapping of the acoustic energy toward the surface of the piezoelectric substrate; and (iii) the electromechanical coupling efficiency of the IAW is very close to that of the surface acoustic wave (SAW) along the bare LiNbO₃ half-space. The numerical predictions were experimentally assessed for some SU-8 layer thicknesses and overcoat material types. The propagation of the IAWs was experimentally measured in LiNbO₃/SU-8/fused silica, LiNbO₃/SU-8/(001)Si, and LiNbO₃/SU-8/c-Al₂O₃ structures for an SU-8 layer about 15 µm thick; the velocities of the IAWs were found in good agreement with the theoretically calculated values. Although the interest in IAWs was born many years ago for packageless applications, it can currently be renewed if thought for applications in microfluidics. Indeed, the IAWs may represent a valid alternative to standing SAWs, which are strongly attenuated when travelling beneath the walls of polydimethylsiloxane (PDMS) microfluidic channels for continuous flow particle manipulation, provided that the channel is excavated into the overcoating. Full article

Low-cost electrochemical methodologies for the determination of L-ascorbic acid (vitamin C) and the analysis of juices are developed based on its electro-oxidation on carbon screen-printed electrodes. A novel chronoamperometric methodology is developed for the quantification of L-ascorbic acid in fruit juices. The proposed method stands out for its simplicity and rapidity, demonstrating its efficacy in determining L-ascorbic acid content in various fruit juices. Notably, the results obtained with this chronoamperometric approach are compared with those yielded by chromatography, with no significant differences between the two methods being found. Additionally, an electronic tongue is developed for the differentiation of juices based on the square wave voltammetric signals. Full article

Accurate measurement of ocean wave parameters is critical for applications including ocean modeling, coastal engineering, and disaster management. This article introduces a novel global navigation satellite system (GNSS) drifting buoy for surface wave measurements that addresses the challenges of performing real-time, high-precision measurements and realizing cost-effective large-scale deployment. Unlike traditional approaches, this buoy uses the kinematic extension of the variometric approach for displacement analysis stand-alone engine (Kin-VADASE) velocity measurement method, thus eliminating the need for additional high-precision measurement units and an expensive complement of satellite orbital products. Through testing in the South China Sea and Laoshan Bay, the results showed good consistency in significant wave height and main wave direction between the novel buoy and a Datawell DWR-G4, even under mild wind and wave conditions. However, wave mean period disparities were observed partially because of sampling frequency differences. To validate this idea, we used Joint North Sea Wave Project (Jonswap) spectral waves as input signals, the bias characteristics of the mean periods of the spectral calculations were compared under conditions of identical input signals and gradient-distributed wind speeds. Results showed an average difference of 0.28 s between the sampling frequencies of 1.28 Hz and 5 Hz. The consequence that high-frequency signals have considerable effects on the mean wave period calculations indicates the necessity of the buoy’s high-frequency operation mode. This GNSS drifting buoy offers a cost-effective, globally deployable solution for ocean wave measurement. Its potential for large-scale networked ocean wave observation makes it a valuable oceanic research and monitoring instrument. Full article

We revisit the seminal model of glycolysis first proposed by Sel’kov more than fifty years ago. We investigate the onset of instabilities in biological systems described by the Sel’kov model in order to determine the conditions of the model parameters that lead to bifurcations. We analyze the glycolysis reaction under the circumstances when the diffusivity of both ATP and ADP reactants are taken into account. We estimate the critical value of the model’s single compact dimensionless parameter, which is responsible for the onset of reaction instability and the system’s symmetry breaking. It appears that it leads to spatial inhomogeneities of reactants, leading to the formation of standing waves instead of a homogeneous distribution of ATP molecules. The consequences of this model and its results are discussed in the context of the Warburg effect, which signifies a transition from oxidative phosphorylation to glycolysis that is correlated with the initiation and progression of cancer. Our analysis may lead to the selection of therapeutic interventions in order to prevent the symmetry-breaking phenomenon described in our work. Full article

Fault location estimation in transmission lines is critical for power system reliability. Various methods have been developed for this purpose, among which transient frequency spectrum analysis (TFSA) stands out as a recent method based on travelling wave (TW) theory. TFSA determines the fault location by analyzing the frequency spectrum of transient currents and/or voltages at the instant of the fault, offering advantages such as independence from fault impedance and the ability to locate faults with one-side measurements. Despite its success in fault location, TFSA has several considerations that warrant detailed investigation. This study explores the effects of source inductance, series compensation, fault arc, and current transformer (CT) characteristics on transient frequencies. Additionally, the impact of noise on TFSA results is examined. The new proposed source inductance compensation method can reduce the error of 6.55% to 0.88%, where the same error can be reduced to 3.45% with the compensation method given in previous study. Strategies to enhance accuracy are discussed and compared to previous studies, including a proposed detection approach providing appropriate data size and precise wave propagation speed calculations. These findings contribute to a deeper understanding of TFSA’s limitations and inform practical improvements for fault location accuracy in power transmission systems. Full article

To advance wave energy devices towards commercialization, it is essential to optimize their design to enhance system performance. Additionally, a thorough economic evaluation is crucial for making these technologies competitive with other renewable energy sources. This study focuses on the techno-economic optimization of an innovative inertial system, the so-called SWINGO system, which is based on gyropendulum technology. SWINGO stands out due to its high energy efficiency in multi-directional installation sites, where wave directions vary significantly throughout the year. The study introduces the application of a multi-objective Evolutionary Algorithm (EA), specifically the Non-dominated Sorting Genetic Algorithm II (NSGA-II), to optimize the techno-economic performance of the SWINGO system. This approach aims to identify optimal design parameters that maximize energy extraction while considering economic viability. By deriving a Pareto frontier, a set of optimal devices is selected for further analysis. The performance of the SWINGO system is also compared to an alternative (mono-directional) inertial wave energy converter, the Inertial Sea Wave Energy Converter (ISWEC), to highlight the differences in techno-economic outcomes. Both systems are evaluated at two different installation sites: Pantelleria island and the North Sea in Denmark, with a focus on the directional wave scatter at each location. Full article

In the field of thermal non-destructive testing and evaluation (TNDT&E), active thermography gained popularity due to its fast wide-area monitoring and remote inspection capability to assess materials without compromising their future usability. Among the various active thermographic methods, pulse compression-favorable frequency-modulated thermal wave imaging stands out for its enhanced detectability and depth resolution. In this study, an experimental investigation has been carried out on a hardened steel sample used in the ship building industry with a flat-bottom-hole-simulated defect using the frequency-modulated thermal wave imaging (FMTWI) technique. The defect detection capabilities of FMTWI have been investigated from various statistical post-processing approaches and compared by taking the signal-to-noise ratio (SNR) as a figure of merit. Among various adopted statistical post-processing techniques, pulse compression has been carried out using different methods, namely the offset removal with polynomial curve fitting and principal component analysis (PCA), which is an unsupervised learning approach for data reduction and offset removal with median centering for data standardization. The performance of these techniques was assessed through experimental investigations on hardened steel specimens used in ship building to provide valuable insights into their effectiveness in defect detection capabilities. Full article

This work studies an inhomogeneous generalized Hartree equation with inverse square potential. The purpose is to prove the existence and strong instability of inter-critical standing waves. This means that there are infinitely many data near to the ground state, such that the associated solution blows-up in finite time. The proof combines a variational analysis with the standard variance identity. The challenge is to deal with three difficulties: the singular potential ${\left|x\right|}^{-2}$, an inhomogeneous term ${\left|x\right|}^{-\lambda }$, and a non-local source term. Full article

This article is devoted to the study of microwave-absorbing properties of Co-C coating applied by magnetron sputtering. This article presents the main results of the manufacturing of a Co-C coating by magnetron sputtering, and the evaluation of experimental and computational research data on the relationship between the structure and properties of the obtained films. The structure of Co-C systems has been modeled to control the resulting structures using X-ray diffraction analysis. The structural-phase state of the resulting thin-film Co-C systems and the microwave-absorbing properties of coatings were studied using the transmission line method, consisting of a vector network analyzer, an air coaxial line, a software program, and an external computer. It has been established that on the resulting Co-C film the reflection coefficient in the frequency range of 8.2–12.4 GHz varies in the range of 900 → 718 mU, with reflection losses of −0.86 → −2.57 dB, and a standing wave coefficient of 19 → 6.8. An analysis of the obtained data indicates the presence of losses of electromagnetic energy in the studied frequency range. Full article