Search Results (5,706)

Background: Right anterior mini-thoracotomy has gained increasing popularity as a preferred approach for mitral valve surgery due to its numerous advantages. This study aims to evaluate the safety and efficacy of this technique in elderly patients. Methods: Between January 2010 and November 2024, a total of 4092 adult patients underwent mitral valve repair or replacement at our institution. Of these, 1687 patients were treated using a minimally invasive approach. This analysis focuses on elderly patients aged 75 years and older (n = 402), further subdivided into two groups: 75–79 years (n = 253) and 80 years and older (n = 149). Results: The study population comprised 49.8% male patients. A small percentage (1.7%) had a history of endocarditis, and 6.5% had undergone prior cardiac surgery. The median logistic EuroSCORE was 7.68 (IQR 5.83–11.00), and the median EuroSCORE II was 2.75 (1.71, 4.40). Alternative cannulation strategies, guided by AngioCT scans, can expand the applicability of this technique to patients unsuitable for femoral cannulation. Median durations for cardiopulmonary bypass (CPB) and aortic cross-clamping were 99.5 and 80.0 min, respectively. Median ventilation time was 7 h, and the median ICU stay was 2 days. Atrial fibrillation was the most common postoperative complication (20.9%). A significant proportion of patients (47.8%) required blood transfusions, and 3.0% needed re-exploration for bleeding. The in-hospital mortality rate was 3.7%, with 7 (1.7%) patients requiring postoperative dialysis and 5 (1.2%) experiencing sepsis and multiple organ failure. Patients aged 80 years and older exhibited worse renal function and higher EuroSCOREs compared to the younger group (p < 0.001). However, they had shorter CPB (p = 0.004) and cross-clamp times (p = 0.001) and underwent a higher proportion of valve replacements (p = 0.003). Rates of major complications and in-hospital mortality were comparable between the two age groups. Logistic regression analysis identified the logistic EuroSCORE as the only significant preoperative risk factor (p = 0.001). Conclusions: Right anterior minithoracotomy is a safe and reproducible surgical approach, even in elderly patients, promoting faster recovery with a lower risk of complications. Among patients aged >80 years, despite higher comorbidities and elevated EuroSCORE II, in-hospital outcomes are comparable to those aged 75–79 years. Full article

Hydrogen energy is considered a crucial clean energy carrier for replacing fossil fuels in the future. Liquid hydrogen (LH₂), with its economic advantages and high purity, is central to the development of future hydrogen refueling stations (HRSs). However, leakage poses significant fire and explosion risks, challenging its safe industrial use. In this study, a numerical model of LH₂ leakage at an HRS in Chongqing was established using Computational Fluid Dynamics (CFD) software. The diffusion law of a flammable gas cloud (FGC) was examined under the synergistic effect of the leakage direction, rate, and wind speed of an LH₂ storage tank in an HRS. The phase transition of LH₂ presents dual risks of combustion and frostbite owing to the spatial overlap between low-temperature areas and FGCs. The findings revealed that the equivalent stoichiometric gas cloud volume (Q9) reached 685 m³ in the case of crosswind leakage, with the superimposed effect of reflected waves from the LH₂ transport vehicle resulting in a peak explosion overpressure of 0.61 bar. The low-temperature hazard area and the FGC (with a concentration of 30–75%) show significant spatial overlap. These research outcomes offer crucial theoretical underpinning for enhancing equipment layout optimization and safety protection strategies at HRSs. Full article

The first part of this study is related to the search of fixed points for (E)-operators (Garcia-Falset operators), in the Banach setting, by means of a three-step iteration procedure. The main results reveal some conclusions related to weak and strong convergence of the considered iterative scheme toward a fixed point. On the other hand, the usefulness of the S_n iterative scheme is once again revealed by demonstrating through numerical simulations the advantages of using it for solving the problem of the maximum modulus of complex polynomials compared to standard algorithms, such as Newton, Halley, or Kalantary’s so-called B₄ iteration. Full article

This study presents a comprehensive numerical simulation and thermal performance analysis of a novel modular floating solar still system, featuring integrated heat-pipe vacuum tube collectors, designed for seawater desalination. This innovative system—subject of International Patent Application WO 2023/062261 A1—not only aims to enhance efficiency and scalability beyond traditional solar stills, but also addresses the significant environmental challenge of concentrated brine discharge inherent in conventional desalination methods. The study evolved from an initial theoretical model to a rigorous dynamic thermal model, validated using real hourly meteorological data from Málaga, Andalusia, Spain. This modelling approach was developed to quantify heat transfer mechanisms and accurately predict system performance. The refined hourly simulation forecasts an annual freshwater production of approximately 174 L per unit. Notably, a preliminary economic assessment estimates the Cost of Produced Water per Litre (CPL) at 0.7509 EUR/litre, establishing a valuable baseline for future optimisation. These findings underscore the critical importance of dynamic hourly simulations for realistic performance prediction and validate the technical and preliminary economic feasibility of this novel approach. The system’s projected output, modular floating design, and significant environmental advantages position it as a promising and sustainable solution for freshwater production, particularly in coastal regions and sensitive marine ecosystems. This work provides a solid foundation for future experimental validation, cost optimisation, and scalable implementation of renewable energy-driven desalination. Full article

Acoustic Emission tomography (AET) has the potential to visualize damage in existing structures, contributing to structural health monitoring. Further, AET requires only the arrival times of elastic waves at sensors to identify velocity distributions, as source localization based on ray-tracing is integrated into its algorithm. Thus, AET offers the advantage of easy acquisition of measurement data. However, accurate source localization requires a large number of elastic wave source candidate points, and increasing these candidates significantly raises the computational resource demand. Lagrange Interpolation has the potential to reduce the number of candidate points, optimizing computational resources, and this potential has been validated numerically. In this study, AET incorporating Lagrange Interpolation is applied to identify the velocity distribution in a defective concrete plate, validating its effectiveness using measured wave data. The validation results show that the defect location in the concrete plate is successfully identified using only 36 source candidates, compared to the 121 candidates required in conventional AET. Furthermore, when using 36 source candidates, the percentage error in applying Lagrange Interpolation is 8.4%, which is significantly more accurate than the 25% error observed in conventional AET. Therefore, it is confirmed that AET with Lagrange Interpolation has the potential to identify velocity distributions in existing structures using optimized resources, thereby contributing to the structural health monitoring of concrete infrastructure. Full article

Numerous studies on specific cannabis compounds (cannabinoids and phenolic acids) have demonstrated their therapeutic potential, with their administration methods remaining a key research focus. Transdermal drug delivery (TDD) systems are gaining attention due to their advantages, such as painless administration, controlled release, direct absorption into the bloodstream, and its ability to bypass hepatic metabolism. The thin films obtained via pulsed laser deposition consist of micro- and nanoparticles capable of migrating through skin pores upon contact. This study investigates the interaction of phenolic compounds in hemp seeds with pulsed laser beams. The main goal is to achieve the ablation and deposition of these compounds as thin films suitable for TDD applications. The other key objective is optimizing laser energy to enhance the industrial feasibility of this method. Thin layers were deposited on glass and hemp fabric using dual pulsed laser (DPL) ablation on a compressed hemp seed target held in a stainless steel ring. The target was irradiated for 30 min with two synchronized pulsed laser beams, each with parameters of 30 mJ, 532 nm, pulse width of 10 ns, and a repetition rate of 10 Hz. Each beam had an angle of incidence with the target surface of 45°, and the angle between the two beams was also 45°. To improve laser absorption, two approaches were used: (1) HS-DPL/glass and HS-DPL/hemp fabric, in which a portion of the stainless steel ring was included in the irradiated area, and (2) HST-DPL/glass and HST-DPL/hemp fabric—hemp seeds were mixed with turmeric powder, which is known to improve laser interaction and biocompatibility. The FTIR and Micro-FTIR spectroscopy (ATR) performed on thin films compared to the target material confirmed the presence of hemp-derived phenolic compounds, including tetrahydrocannabinol (THC), cannabidiol (CBD), ferulic acid, and coumaric acid, along with other functional groups such as amides. The ATR spectra have been validated against Gaussian 6 numerical simulations. Scanning electron microscopy (SEM) and substance transfer tests revealed the microgranular structure of thin films. Through the analyzes carried out, the following were highlighted: spherical structures (0.3–2 μm) for HS-DPL/glass, HS-DPL/hemp fabric, HST-DPL/glass, and HST-DPL/hemp fabric; larger spherical structures (8–13 μm) for HS-DPL/glass and HST-DPL/glass; angular, amorphous-like structures (~3.5 μm) for HS-DPL/glass; and crystalline-like structures (0.6–1.3 μm) for HST-DPL/glass. Microparticle transfer from thin films on the hemp fabric to the filter paper at a human body temperature (37 °C) confirmed their suitability for TDD applications, aligning with the “whole plant medicine” or “entourage effect” concept. Granular, composite, thin films were successfully developed, capable of releasing microparticles upon contact with a surface whose temperature is 37 °C, specific to the human body. Each of the microparticles in the thin films obtained with the DPL technique contains phenolic compounds (cannabinoids and phenolic acids) comparable to those in hemp seeds, effectively acting as “microseeds.” The obtained films are viable for TDD applications, while the DPL technique ensures industrial scalability due to its low laser energy requirements. Full article

The rapid expansion of device connectivity and the increasing demand for data traffic have become pivotal aspects of our daily lives, especially within the Internet of Things (IoT) ecosystem. Consequently, operators are striving to identify the most innovative and robust solutions capable of accommodating these escalating requirements. The emergence of the sliced fifth-generation mobile network (sliced 5G) offers a promising architecture that leverages a novel Radio Access Technology known as New Radio (NR), promising significantly enhanced data rate experiences. By integrating the network slicing (NS) architecture, greater flexibility and isolation are introduced into the preexisting infrastructure. The isolation effect of NS is particularly advantageous in mitigating interference between slices, as it empowers each slice to function independently. This paper addresses the user association challenge within a sliced 5G (NR)-IoT network. To this end, we present an Unconstrained-Markov Decision Process (U-MDP) model formulation of the problem. Subsequently, we propose the U-MDP association algorithm, which aims to determine the optimal user-to-slice associations. Unlike existing approaches that typically rely on static user association or separate optimization strategies, our U-MDP algorithm dynamically optimizes user-to-slice associations within a sliced 5G-IoT architecture, thereby enhancing adaptability to varying network conditions and improving overall system performance. Our numerical simulations validate the theoretical model and demonstrate the effectiveness of our proposed solution in enhancing overall system performance, all while upholding the quality of service requirements for all devices. Full article

Digital holographic microscopy (DHM) provides numerous advantages, such as noninvasive sample analysis, real-time dynamic detection, and three-dimensional (3D) reconstruction, making it a valuable tool in fields such as biomedical research, cell mechanics, and environmental monitoring. To achieve more accurate and comprehensive imaging, it is crucial to capture detailed information on the microstructure and 3D morphology of samples. Phase processing of holograms is essential for recovering phase information, thus making it a core component of DHM. Traditional phase processing techniques often face challenges, such as low accuracy, limited robustness, and poor generalization. Recently, with the ongoing advancements in deep learning, addressing phase processing challenges in DHM has become a key research focus. This paper provides an overview of the principles behind DHM and the characteristics of each phase processing step. It offers a thorough analysis of the progress and challenges of deep learning methods in areas such as phase retrieval, filtering, phase unwrapping, and distortion compensation. The paper concludes by exploring trends, such as ultrafast 3D holographic reconstruction, high-throughput holographic data analysis, multimodal data fusion, and precise quantitative phase analysis. Full article

Ultrasonic testing (UT) is a vital nondestructive testing (NDT) technique used to evaluate the integrity of materials and structures. However, conventional excitation signals often suffer from significant attenuation in highly attenuative materials, resulting in low signal energy and poor signal interpretation. Coded excitation techniques, such as the Barker code and the complementary Golay code (CGC), have been used to enhance signal energy and signal-to-noise ratio. Yet, Barker codes are limited by short sequence lengths, while CGC requires two transmission events, reducing time efficiency. This paper proposes a novel excitation method: the Barker-convolved mutually orthogonal Golay complementary code (BMOGCC). By convolving the Barker code with the mutually orthogonal Golay complementary code (MOGCC), BMOGCC combines the advantages of both, including flexibility in code length, improved signal amplitude, low sidelobe levels, and enhanced time efficiency. Performance was evaluated using numerical simulations and laboratory experiments, with key indices including the peak sidelobe level (PSL), mainlobe gain (MG), and temporal resolution. The results show that BMOGCC achieves a significantly higher MG than either the Barker code or MOGCC alone while maintaining a low PSL and preserving the temporal resolution. These findings demonstrate that BMOGCC is effective and efficient for coding excitation signals in ultrasonic testing, offering improved signal quality and measurement time efficiency. Full article

The dynamic fracture of rocks under impact loads has many engineering applications such as rock blasting. This study reviews the recent achievements of investigating rock dynamic fracturing and its application in rock blasting using computational mechanics methods and highlights the prospects of modelling them with a hybrid finite-discrete element method (HFDEM) originally developed by the authors. The review first summarizes the peculiarities of rock dynamic fracturing compared with static fracturing, which are that the physical-mechanical properties of rocks, including stress wave propagation, strength, fracture toughness, energy partition and cracking mechanism, depend on loading rate. Then the modelling of these peculiarities and their applications in rock blasting using fast developing computational mechanics methods are reviewed with a focus on the advantages and disadvantages of prevalent finite element method (FEM) as representative continuum method, discrete element method (DEM) as representative discontinuum method and combined finite-discrete element (FDEM) as representative hybrid method, which highlights FDEM is the most promising method for modelling rock dynamic fracture and blasting application as well as points out the research gaps in the field of modelling the dynamic fracture of rocks under impact loads. After that, the progress of shortening some of these gaps by developing and applying HFDEM, i.e., the authors’ version of FDEM, for modelling rock dynamic fracture and applications in rock blasting are reviewed, which include the features of modelling the effects of loading rate; stress wave propagation, reflection and absorbing as well as stress wave-induced fracture; explosive-rock interaction including detonation-induced gas expansion and flow through fracturing rock; coupled multiaxial static and dynamic loads; heterogeneous rock and rock mass with pre-existing discrete fracture network; and dynamic fracturing-induced fragment size distribution. Finally, the future directions of modelling the dynamic fracture of rocks under impact loads are highlighted and a systematic numerical approach is proposed for modelling rock blasting. Full article

Acoustic emission (AE) testing is a non-destructive method used in various applications. In our work we demonstrate its capabilities and potential in studying the functional properties of physical vapor deposited (PVD) coatings. The goal was to classify the coating damage during indentation testing more objectively by quantifying specific imprint features. The AE response was systematically recorded in nine sample conditions and 27 individual imprints, allowing us to identify correlations between the numerical values derived from the SEM observations and the characteristics of the AE signal. An increase in the delaminated coating area was found to correspond to an exponential increase in the AE signal energy. These findings suggest that AE analysis could reduce the reliance on SEM-based evaluation and help accelerate systematic research in the field of PVD coatings. The advantages of AE testing are discussed and conclusions for practical applications are provided. Full article

Multi-rotor ducted propellers, which integrate the high-efficiency characteristics of ducted propellers with the layout flexibility and safety advantages of distributed propulsion, are extensively utilized in the propulsion systems of low-altitude transport systems and large-scale unmanned aerial vehicles. This study numerically investigates the effects of spanwise distance, streamwise distance, rotational consistency, and rotational phase gap on the unsteady aerodynamic characteristics of multi-rotor ducted propellers under hovering conditions. A parameterized numerical computation model and an Aligned Rank Transform Analysis of Variance (ART-ANOVA) method suitable for small datasets exhibiting regular patterns were developed. Initially, numerical simulations investigated the aerodynamic performance of multi-rotor ducted propeller models with varying layout parameters. The aerodynamic coefficients of the propellers monotonically decrease as the layout spacing increases; however, the change trends differ. Aerodynamic interference reduces the airflow velocity and influences the distribution of high-pressure zones, consequently impacting thrust and efficiency. Subsequently, this paper examined the coupled effects of two rotational characteristics. The relationship between propeller aerodynamic performance and rotational phase gap exhibits distinct trigonometric function characteristics. The presence of the duct mitigates the mutual interference between blades, thereby altering the amplitude and phase of these characteristics. Finally, an ART-ANOVA method was employed to quantify the main and interaction effects, revealing that rotational consistency has a dominant influence on all aspects of aerodynamic performance. Insights into aerodynamic performance are crucial for advancing low-altitude transport systems that utilize ducted propeller propulsion systems. 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

DC arcs are widely used in many fields such as shipbuilding, machinery manufacturing, and aerospace due to their advantages of high energy density, simple structure, and low price. However, there are few studies on the sensitivity of the arc pressure and temperature fields to current and protective gas flow rate. In order to solve this problem, this paper establishes a numerical model for the coupling of DC arc electric–thermal–flow multi-physical fields. Based on this model, the variation rules of the arc temperature, pressure, and potential field with current or protective gas flow rate are studied, respectively, when the current is 100–600 A or the gas flow rate is 18–48 L/min. The results show that the current is the most important factor in the sensitivity of the arc temperature and potential field to the current and protective gas flow rate. With the increase in current, the Joule heat power increases significantly, and the arc central temperature shows a nonlinear increase to 27,000 K. With increasing current, the peak of the pressure field gradually shifts to the region below the top of the wire arc, and the highest pressure increases by 14 times. When the current is small, the increase in argon flow rate can inhibit the spreading of the temperature field by forced convection; when the current is large, the arc contraction with an increasing argon flow rate leads to an anomalous increase in the arc-central temperature. In addition, the energy accumulation mechanism in the strong-current–high-flow-rate coupling region is also revealed, a coupled mathematical model of arc contraction and turbulent loss under the Lorentz force is constructed, and the thermodynamic properties of the arc under the coupling of multi-physical fields are elucidated. Full article

This paper investigates a slow–fast stochastic reaction–diffusion–advection equation with Hölder-continuous coefficients, where the irregularity of the coefficients presents significant analytical challenges. Our approach fundamentally relies on techniques from Poisson equations in Hilbert spaces, through which we establish optimal strong convergence rates for the approximation of the averaged solution by the slow component. The key advantage that this paper presents is that the coefficients are merely Hölder continuous yet the optimal rate can still be obtained, which is crucial for subsequent central limit theorems and numerical approximations. Full article