Search Results (15,564)

Dielectric and magnetic spherical hollow shells are employed in many applications as standard building units. These structures are commonly subjected to size reduction to obtain a high surface area/volume ratio, a property that is in favor of specific applications. However, the size reduction enhances the importance of physical mechanisms that originate from surfaces, such as the depolarization effect. Here we tackle the problem of dielectric and magnetic spherical hollow shells, consisting of a linear, homogeneous and isotropic parent material, subjected to an external potential, $U_{ext}\left(\mathit{r}\right)$, of any spatial form (either dc (static) or ac of low-frequency (quasistatic limit)). By applying the method-of-linear-recursive-solution (MLRS) to the Laplace equation, we calculate analytically the internal, $U_{int}\left(\mathit{r}\right)$, and total, $U_{tot}\left(\mathit{r}\right)$, potentials in respect to the external one, $U_{ext}\left(\mathit{r}\right)$. From $U_{int}\left(\mathit{r}\right)$ and $U_{tot}\left(\mathit{r}\right)$ we calculate all relevant scalar and vector physical entities of interest. The MLRS unveils straightforwardly the existence of two distinct depolarization factors, $N_l=l/(2l+1)$ and $N_{l+1}=(l+1)/(2l+1)$, both depending on the degree, $l$, however not on the order, $\mathrm{m}$, of the mode of the external potential, $U_{ext}^{(l,m)}\left(\mathit{r}\right)$. These depolarization factors, $N_l$ and $N_{l+1}$, originate from the outer, $r=\mathrm{b}$, and inner, $r=\mathrm{a}$, surfaces and are accompanied by two extrinsic susceptibilities, ${\chi }_{e,l}^{ext}={\chi }_e^{}/(1+N_l{\chi }_e^{})$ and ${\chi }_{e,l+1}^{ext}={\chi }_e^{}/(1+N_{l+1}{\chi }_e^{})$, respectively. Importantly, $N_l+N_{l+1}=1$, irrespective of the degree, $l$, as it should. The properties of spherical hollow shells are investigated through analytical modeling and detailed simulations, with emphasis on application-relevant scenarios including resonance phenomena in scattering, quantitative materials characterization, and shielding/distortion. The generic MLRS strategy provides a flexible and reliable route for analyzing depolarization processes in other dielectric and magnetic building-unit geometries encountered in practice. Full article

Timely classification of cardiovascular diseases is crucial to improve medical outcomes. Emerging remote patient monitoring systems help achieve this by enabling continuous monitoring of electrocardiogram signals in home environments. However, these systems struggle with unique challenges like missing genuine medical emergencies, rising energy demands, scalability challenges, handling vast medical databases, data processing delays, and safeguarding patient records. To overcome these challenges, we propose a single framework with three main phases: (a) an embedded hardware-driven K-Nearest Neighbor (KNN)-assisted real-time ECG monitoring and classification method; (b) a differentiated communication strategy (DCS) formed with a priority-based ECG data packaging framework and multi-layered security protocols; and (c) a multi-level blockchain network (MLBN) architecture armed with adaptive security mechanisms and real-time cross-chain medical data communication bridges. Simulations are conducted using the ECG signals (1000 fragments) dataset and the Ganache Ethereum development framework. The classification accuracies obtained for patient urgent categories U1 to U5 are 91.43%, 95.71%, 94.23%, 90.00%, and 91.43%, respectively. The performance evaluation results of the KNN-guided classification method, along with DCS and MLBN simulation results obtained from average gas consumption analysis, confirms reliability and viability of our framework, while also revolutionizing remote patient monitoring technology and addressing critical challenges in existing systems. Full article

The crosslinked binders formed by using glycidyl azide polymer (GAP) as the binder matrix and bis-propargyl succinate (BPS) as the curing agent have good application prospects in the field of solid propellants. Aiming at the shortcomings of traditional experimental research, such as high cost, and molecular dynamics (MD) simulation, which are time-consuming for complex combination problems, this study will realize accurate prediction of the mechanical properties of binders through machine learning (ML) based on the molecular simulation dataset. Firstly, 273 sets of GAP-BPS binder models under different conditions were formed based on 21 crosslinking degrees and 13 temperatures, and MD simulation and mechanical property simulation were carried out. Then, the initial conditions of molecular simulation (crosslinking degree, temperature) and structural parameters (free volume) were taken as features, and the bulk modulus and shear modulus were taken as labels to form the dataset. Three machine learning models were trained and evaluated based on this dataset to test their prediction performance. Based on the cross-validation results, the Tabular Prior Data Fitting Network (TabPFN) exhibits the highest average prediction values (the average R² for bulk modulus and shear modulus were 0.9684 and 0.8827, respectively). But the significance analysis reveals that TabPFN significantly outperforms the RF model only in predicting bulk modulus. In subsequent prediction tasks with smaller datasets, TabPFN achieves superior average prediction values compared with RF and XGBoost. Full article

Metal–organic frameworks (MOFs) are a versatile class of hybrid crystalline materials that have emerged as promising candidates for a broad range of applications. γ-cyclodextrin MOFs (γ-CD-MOFs) represent an innovative subgroup of MOFs constructed from “edible” γ-CD ligands coordinated with biocompatible metal ions to form an extended porous structure. Owing to their unique characteristics such as their “green” origin, biodegradability, and biocompatibility they became a promising platform for drug delivery applications. Structurally, γ-CD-MOF possess a body-centered cubic structure with dual-mode porosity, enabling the simultaneous encapsulation of hydrophilic and hydrophobic drugs. Such structural features contribute to high loading capacity, tunable release behavior, and enhanced stability of incorporated drugs. In this review, we comprehensively discuss the structural features of γ-CD-MOF, synthesis strategies, crystals size and morphology control, activation and drying techniques, and drug encapsulation approaches. We further address computational and simulation approaches used to predict and optimize drug-framework interactions, as well as post- synthetic modifications aimed at enhancing stability and functionality. The diverse pharmaceutical applications of γ-CD-MOFs are examined, including the delivery of small molecules, macromolecules, multi-drug systems, and emerging pulmonary formulations. Additionally, we examine biocompatibility and safety considerations and current limitations related to aqueous stability, industrial-scale production, and reproducibility. Finally, this review highlights recent progress and underlines future perspectives, emphasizing innovations such as fast drug-loaded MOF formation via spray-drying, co-delivery strategies, and vaccine-oriented formulations. Together, these insights highlight the potential of γ-CD-MOFs to shape the next generation of multifunctional drug delivery systems across interdisciplinary fields. Full article

This study presents a comparison between the results of process parameter optimization for the deep drawing of an AA5754-O automotive fuel tank, which utilizes two different objective functions. The first objective function is the maximum thinning percentage (max. %Thinning) of the formed part, which is a conventional formability index. The second is Q-value, a metric derived from the Thinning Limit Diagram that accounts for both necking-prone (excessive thinning) and wrinkling-prone (thickening) regions. The experiments were conducted using finite element simulation to model the forming behavior under an inscribed central composite design within the response surface methodology. Three process parameters, which are well known to be important for controlling material flow and achieving a balance between wrinkling and excessive thinning in deep drawing, were varied: blank holder pressure, the height of the male drawbead, and the radius of the female drawbead. Refined second-order response surface models were developed for both objective functions. Optimization based on the response surface models showed that, for the max. %Thinning objective function, the final part exhibited 19.46% maximum thinning but suffered from substantially higher wrinkling, as indicated by a maximum thickening of 36.39%. In contrast, the Q-value-based optimization resulted in a more balanced formability condition, with maximum thinning of 21.74% and maximum thickening of 13.17%. Moreover, the normalized density of elements in the safe zone of the Thinning Limit Diagram was higher, indicating an improvement in formability robustness. Therefore, this study highlights the limitations of conventional thinning-based optimization and demonstrates the potential of the Q-value as an extended practical quantitative formability tool that can simultaneously address necking and wrinkling in sheet metal forming, as presented through the studied automotive fuel tank on behalf of complex components. Full article

The low separation efficiency of alkali/surfactant/polymer (ASP)-flooding-produced water, attributed to its high emulsification, high viscosity, and surfactant enrichment, presents a significant treatment challenge. To evaluate the effects of flotation unit structure on internal flow field characteristics and the separation performance of oil and suspended solids in a dissolved air flotation–sedimentation tank, this study conducted CFD numerical simulations. The results demonstrate that with 40 gas injection ports, the flow field achieves optimal uniformity and stability: the oil removal rate reaches 68.1%, and the suspended solids removal rate reaches 56.6%. Compared to the single-ring and triple-ring configurations, the double-ring gas injection form exhibits better flow continuity, resulting in increased removal rates of 67.6% for oil and 56.7% for suspended solids. At a gas injection ring height of 10,500 mm, the oil layer in the flotation zone remains continuous and stable, while suspended solids settle into a distinct sediment layer at the bottom, enhancing both oil and suspended solids removal efficiencies. On this basis, the optimized structure of the flotation unit was determined. The removal rates of oil and suspended solids were enhanced by approximately 1.8% to 4.8% and 3.5% to 7.0%, respectively, compared to the existing conditions. Full article

This paper investigates the application of cooperative relaying systems with non-orthogonal multiple access (NOMA) in low-altitude intelligent networking-enabled medical Internet of Things (IoT) and analyzes their transmission performance. First, to enhance the communication quality of remote base stations, we deploy a relaying unmanned aerial vehicle (UAV). A two-slot NOMA cooperative transmission mechanism is proposed accordingly. Next, for the NOMA-enhanced UAV-relayed smart healthcare system under Rician fading channels, an exact closed-form expression for the achievable rate is derived using the incomplete Gamma function. Then, to improve computational efficiency, a low-complexity approximation method based on Gauss–Chebyshev quadrature is designed, overcoming the high complexity of the exact expression. Finally, the simulation results validate a close match between the proposed approximation and the exact values (average approximation error below 6.17%), and demonstrate superior achievable rate performance compared to three state-of-the-art schemes. Full article

Flexible circular shafts are critical components for power transmission in engineering systems. However, they are susceptible to complex three-dimensional coupled vibrations under multidirectional excitations, which can compromise operational stability and lead to structural fatigue. To address this issue, this paper presents an active control method for the three-dimensional vibration of a piezoelectrically driven flexible circular shaft via a fuzzy adaptive PID algorithm. The study begins by establishing a dynamic model of the system based on the Euler–Bernoulli beam theory and Lagrange equation. This model forms the foundation for the design of a fuzzy adaptive PID controller. The accuracy of the developed model is then validated through simulations and experiments. Subsequently, active vibration control (AVC) experiments are carried out to evaluate the vibration attenuation effectiveness of various control strategies (including a conventional PID controller as the benchmark for comparison) under different types of excitations applied at the shaft root. The results demonstrate that the proposed active control method has superior control performance, and exhibits excellent vibration suppression performance, especially under bidirectional excitation at the natural frequency, where the vibration suppression ratios in the two orthogonal directions reach 93.03% and 92.09%, respectively. Full article

The increasing availability of microwave bistatic remote sensing data highlights the need for reliable and computationally efficient scattering models to support data interpretation, system design, and mission planning. This is particularly relevant in urban and maritime environments, where the electromagnetic (EM) interaction between buildings and ships with the surrounding environment significantly affects the observed bistatic signatures. This paper presents a fully analytical model for EM bistatic scattering from a canonical target, represented as a parallelepiped with smooth dielectric faces located over a lossy random rough surface. The formulation is developed within the framework of the Kirchhoff Approximation and accounts for both single- and multiple-bounce scattering mechanisms arising from the mutual interaction between the target and the underlying surface. Reflections from the target walls are modeled using the Geometrical Optics solution, while scattering from the rough surface is described through the zeroth-order Physical Optics approximation. The resulting closed-form expressions provide both coherent and incoherent components of the scattered field as explicit functions of system and scene parameters. The proposed closed-form model enables fast and reliable evaluation of bistatic scattering from parallelepiped-like structures, such as buildings and large ships interacting with surrounding rough surfaces. This capability is particularly beneficial for the design and optimization of bistatic remote sensing missions in urban and maritime contexts as well as the development and assessment of inversion methods and large-scale analyses. Validation against numerical simulations and experimental results available in the literature demonstrates the effectiveness of the proposed approach across different operating conditions. Full article

To address the instability risk of grid-forming inverters under large power dispatch in low-inertia and low-damping power grids caused by renewable energy integration, based on the grid-forming inverter connected to an infinite bus system model, transient stability under power dispatch is conducted. The power dispatch boundaries constrained by transient stability are analyzed by the inverter’s output power-angle characteristics and the equal area criterion. To enable on-demand power dispatch for the grid-forming inverter, a power ramp scheduling strategy constrained by transient stability is proposed. Furthermore, to overcome the limitations of variable-step ramp scheduling, such as a prolonged transient duration, significant output waveform overshoot, and the need for real-time computation, an improved scheme employing virtual inertia emulation is presented, along with its parameter design methodology for the inertia emulation block. The response time and overshoot can be effectively reduced. Finally, simulations and experiments validate the effectiveness of the proposed equivalent-inertia ramp control scheme in improving system transient stability under power dispatch. Full article

White tea infusion micro-nanoparticles (WTMPs) are important for colloidal stability, but the optimal strategy for their isolation and the mechanisms underlying their stability remain unclear. Here, a multi-indicator TOPSIS strategy was used to optimize ultrafiltration–centrifugation, and the best condition was identified as a 100 kDa membrane, 3000×g, and 20 min. The isolated WTMPs were not merely a concentrated form of white tea colloids (WTCs), but a selectively enriched fraction with remodeled composition, more regular morphology, more ordered intermolecular organization, and improved environmental stability. In particular, gallic acid (GA) was enriched, whereas caffeine (CAF) decreased markedly after isolation. Spectroscopy and molecular dynamics simulations further suggested that GA and CAF played different roles in the protein–polysaccharide network: GA was more favorable for cooperative interfacial stabilization, whereas CAF behaved more like a locally associated ligand. Overall, these results support a composition–structure–stability relationship for WTMPs and provide mechanistic insight into the selective enrichment of GA and the enhanced stability of the isolated micro-nanoparticle fraction. Full article

The harmonic equivalent method is a non-perturbative approach to nonlinear vibration issues, aiming to create linearly coupled systems from coupled vibrations. However, there is still much to be discovered about managing interconnected nonlinear components. This paper examines the nonlinear components of a fractal-connected system and offers suggestions. This paper explores insights into the principles and uses of nonlinear systems in science and engineering by investigating the dynamic behavior of a connected cubic–quintic damping fractal system analytically using an innovative approach to analytical examination. A two-scale transformation and reformulation of the system into fractal form simplify its governing equations for dynamic and stability analysis. Two analytical scopes are presented: one decouples nonlinear systems using weighted averaging functions, and the other converts even nonlinearities into odd terms using El-Dib’s frequency formulas for linear representation, enabling an equivalent linear representation of the system. The resilience of the decoupled system is verified by numerical simulations using Mathematica, which shows high agreement and minimal relative errors. It also accurately reflects dynamic behavior. Additionally, the work uses the bridging techniques of El-Dib and Elgazery to convert a linear damping fractal coupled system into a classical continuous-space form. A scaling fractal factor is made possible by re-expressing the fractal structure using pseudo-dimensional parameters. The linearly linked damping system has an exact analytical solution. The paper provides valuable insights into the design and control of coupled nonlinear oscillatory systems by validating analytical solutions through numerical simulations using Mathematica. Full article

Human cytomegalovirus (HCMV) remains a significant cause of morbidity in immunocompromised patients, necessitating the development of improved antivirals. Using an integrated in silico and in vitro approach, we identified a novel ligand (NL) as a letermovir analog with enhanced binding affinity and reduced cytotoxicity. A pUL56 terminase subunit model generated with AlphaFold 3 was used for the virtual screening of a 15,000-compound library. Among the 73 candidates with structural similarity to letermovir (Tanimoto ≥ 0.6), NL exhibited superior predicted binding affinity (ΔG_bind = −10.7 kcal/mol). In silico toxicity prediction (ProTox 3.0) classified NL as having low toxicity (class 4, LD50 ≈ 1000 mg/kg), which was confirmed in vitro, where NL demonstrated 158-fold less toxic (CC50 = 2.69 mg/mL) in MRC-5 cells than letermovir (0.017 mg/mL). Molecular dynamics simulations over 500 ns revealed that the pUL56-NL complex forms a more thermodynamically stable interaction, with a lower calculated free energy of binding (MMGBSA: −40.89 ± 7.40 kcal/mol vs. −32.76 ± 4.96 kcal/mol) and a narrower free energy landscape. These results establish NL as a promising, low-cytotoxicity candidate with enhanced target engagement, warranting further investigation as a potential anti-HCMV therapeutic. Full article

In response to the pressing need for miniaturized MEMS microphones in wearable technology and mobile devices, and to surmount the technical limitations inherent in conventional piezoelectric microphones, which typically depend on enlarging chip dimensions or decreasing stiffness to attain low resonance frequencies, this study introduces a novel piezoelectric MEMS microphone (PMM) design predicated on a flexibility-enhanced rotating structure. The proposed design utilizes an aluminum scandium nitride (Al_0.8Sc_0.2N) piezoelectric thin film with 20% scandium doping and incorporates four equivalent sensing units formed by four curved cutting lines centrally located on the chip. This configuration employs a nested arrangement of four cantilever beams to substantially increase vibration compliance, thereby effectively lowering the natural frequency without altering the chip’s external size. Three-dimensional finite element simulations reveal that, relative to traditional triangular cantilever beam architectures, the flexibility-enhanced rotating structure reduces the natural frequency from 15.6 kHz to 13.49 kHz while enhancing sensitivity from −44.6 dB to −40 dB. The device was fabricated via a comprehensive microfabrication process and subsequently characterized within a standardized acoustic testing environment. Experimental results indicate that the microphone attains a sensitivity of −43.84 dB at 1 kHz and exhibits a first resonance frequency of 13.5 kHz, closely aligning with simulation predictions. Furthermore, the signal-to-noise ratio (SNR) reaches 58.3 dB across the full range of human-audible frequencies. By leveraging the flexibility-enhanced rotating structure, this work achieves an optimal compromise between elevated sensitivity and reduced resonance frequency within a compact form factor, thereby offering a viable technical solution for the advancement of high-performance miniature acoustic sensors. Full article

High-resolution Köppen–Geiger projections indicate that several cold desert (BWk) regions are likely to transition toward hot desert (BWh) regimes during the twenty-first century, challenging the environmental logic of vernacular architecture. Despite extensive simulation-based research on passive cooling in established BWh contexts, limited attention has been given to climate-type transition zones and to the morphological continuity of traditional housing systems. This study investigates the adaptive capacity of Bukhara’s courtyard houses under projected BWk–BWh reclassification. Employing an analytical generalization approach, the research integrates systematic literature mapping, typological morphological analysis, and a threshold-based compatibility matrix. Findings reveal that climate transition produces a form of morphological discontinuity by weakening diurnal discharge assumptions embedded in high thermal mass systems. However, courtyard typologies retain a resilient passive core when recalibrated through microclimatic amplification strategies. The proposed staged adaptation framework contributes a heritage-sensitive decision model that reconciles climatic performance with spatial integrity, offering transferable guidance for cli-mate-intensifying desert regions. Full article