Search Results (581)

This study presents a pilot methodological investigation of the thermal performance of a Najdi mudbrick dwelling in Ushaiger, Saudi Arabia, using short-term field monitoring and a preliminary digital-twin inspired workflow. Two field campaigns in August and September 2025 measured indoor and outdoor conditions with a portable weather station under severe site constraints, including lack of electrical infrastructure, restricted access, and the use of consumer-grade sensors. The monitored results indicate that the massive earthen walls attenuated part of the outdoor daily temperature swing, but indoor conditions remained very hot: in August, indoor temperatures averaged 38.1 °C, compared with 40.2 °C outdoors, and in September, indoor temperatures averaged 36.3 °C, compared with 36.1 °C outdoors. A simplified IDA ICE model was compared with the monitored indoor temperature over the available windows, and a post-processing affine bias adjustment was tested only as a diagnostic short-window correction rather than as a transferable calibration. Monte Carlo sensitivity analysis was used in an exploratory way. It examined how passive envelope and boundary-related parameters influenced simulated indoor relative humidity, with infiltration emerging as the dominant factor affecting relative humidity dynamics; peak indoor relative humidity increased from about 67% at 0.15 air changes per hour (ACH) to more than 74% at 0.60 ACH, whereas wall thickness had a modest buffering effect. Given the short monitoring duration and field limitations, the study is not presented as a fully validated digital twin but as a feasibility-oriented workflow that combines constrained in situ monitoring with exploratory simulation to support future, longer-term conservation and adaptive reuse research on earthen heritage in hot–arid climates. Full article

The main objective of the present study is to reveal the palette of pigments and the other specific constituent materials as well as the techniques used by the Roman artists to create the mural paintings discovered in the ancient city of Tomis, the modern-day Constanţa, Romania’s largest seaport and a major tourist hub on the Black Sea. This paper is an archeometric study based on the physical, chemical and biological analyses of the archeological Roman mural painting fragments from the ancient city of Tomis dating from the 5th to 6th century A.D. and to our knowledge is among the very few research studies carried out so far on the ancient Roman wall painting discovered in Romania. The methods of scientific investigation employed directly on the archeological fragments, on samples taken from the fragments and on the cross-sections prepared from the samples were: optical microscopy (OM), digital microscopy, X-ray fluorescence spectrometry (XRF) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). Examination and analysis of the archeological mural fragments revealed that the painted fragments consist of ground support and successive layers of color displaying specific characteristics of the artistic technique, such as imitation of marble cladding or meticulous smoothing of the surface to achieve a glossy and compact finish. It was also found that fragments exhibit subtle variations in different colors, identified in general terms, showing seven color tones: cinnabar red, red-violet, red ochre, yellow ochre, white, gray-blue, gray-black and black. The physical–chemical and biological analyses carried out provide the diagnosis and theoretical basis for choosing an appropriate conservation methodology and the correct restoration treatment of the discovered mural painting, with a view to its museum display through exhibition and virtual reconstruction and scientific use by the setting up of a useful database for researchers or specialists in museums on Roman archeology and art. Full article

This paper proposes a hybrid control method for a 6-DOF robot arm using dynamic impedance to achieve stability, high precision, and robustness simultaneously. Conventional impedance control with fixed inertia, viscosity, and stiffness values lacks robustness against changes in working conditions. The proposed method designs an impedance model for the end-effector and performs position control by adding force-based displacement corrections to the target position for force-controlled axes. Dynamic impedance is realized by relating impedance characteristics to joint angles and angular velocities through the final value theorem and quadratic form transient response analysis. MATLAB/Simulink simulations of wall-wiping motion using an RPY-type 6-DOF robot verify the effectiveness of the proposed method. Full article

Supercritical carbon dioxide (sCO₂) is characterized by low viscosity and a peak in specific heat capacity near the pseudo-critical point, making it a promising coolant for microelectronics. However, most existing sCO₂ test rigs are designed for large-scale thermodynamic cycle studies and lack the capability for controlled, localized heat transfer measurements in small channels. This work presents CO₂-SASS (Scientific Assessment of heat transfer in the Supercritical State), a modular, high-pressure test rig designed to measure local heat transfer coefficients and pressure drops in stainless-steel tubes with diameters on the order of 1–3 mm. The system provides independent control of pressure, mass flow and heating, with direct local wall and fluid temperature as well as precise absolute and differential pressure measurements. Particular emphasis is placed on high-accuracy temperature acquisition, including individual thermocouple calibration and cold-junction bias correction. A detailed uncertainty analysis highlights the dominant role of temperature measurement accuracy, especially for small wall–fluid temperature differences near the pseudo-critical point. Full article

To support the long-term monitoring and preventive conservation of linear cultural heritage, this study proposes a UAV-LiDAR DEM-constrained SBAS-InSAR long-term time-series monitoring method to identify the spatiotemporal deformation patterns and risk-sensitive segments of the near-field ground surface along the Huairou Great Wall. Unlike traditional methods, this research is the first to apply high-resolution UAV-derived DEM for topographic correction and phase modeling in the Huairou Great Wall, aiding in long-term ground deformation monitoring. By integrating multi-scale meteorological data such as precipitation, temperature, and humidity, the study systematically analyzes their impact on deformation. The results reveal significant heterogeneity in ground deformation along the Huairou Great Wall, with the Jiankou section identified as a sensitive area. The study shows a clear event-scale correspondence between rainfall and short-term deformation fluctuations, while air temperature and relative humidity exhibit statistical consistency with cumulative deformation, serving as perturbation cues for sensitivity screening but not direct causal attribution. Compared to traditional ground-based monitoring methods, this approach significantly reduces labor and time costs, enabling large-scale, high-precision, long-term monitoring in a shorter period. It provides a technical basis for identifying risk-prone segments along the Great Wall and conducting post-rainfall inspections, providing a reference for the long-term monitoring and preventive protection of linear cultural heritage. Full article

Under high-altitude, low-Reynolds-number conditions, flow instability in confined dual-fan configurations severely limits the propulsion and thermal management efficiency of heavier-than-air aircraft. This study establishes a high-fidelity 3D transient numerical model using curvature-corrected shear stress transport (SST) turbulence modeling, integrated with proper orthogonal decomposition (POD), dynamic mode decomposition (DMD), and nonlinear stability analysis to investigate rotational direction control mechanisms. Results indicate that co-rotating configurations trigger intense low-frequency pulsations and significant flow skewness due to wall-adhesion effects. Conversely, the counter-rotating layout reconstructs vortex topology by forming a strong interaction shear layer, which enhances local momentum exchange and suppresses large-scale coherent structures. While counter-rotation exhibits a higher initial growth rate, its significantly enhanced nonlinear aerodynamic damping forces the flow into a low-amplitude quasi-steady state, reducing inlet non-uniformity by 74% and increasing mass flow by 5.19%. These findings clarify the physical mechanisms of vortex interference in regulating stability and provide critical design insights for optimizing compact propulsion systems in heavier-than-air high-altitude platforms, such as long-endurance UAVs. Full article

An advanced frequency study in thick-walled functionally graded material (FGM) spherical shells is investigated with advanced shear correction. The values of advanced shear correction can be greater than one, be a negative value, and be affected by a nonlinear term of third-order shear deformation theory (TSDT) of displacements, FGM power law index, and temperature. It is novel and interesting to consider using TSDT and advanced shear correction to derive a simple homogeneous equation with reasonable simplifications into a symmetrical sparse matrix subjected to free vibration. The zero determinant of the symmetrical sparse matrix can be expressed to calculate the natural frequency by Newton’s method. The parameter effects of advanced shear correction, a nonlinear TSDT term, temperature, and the FGM power-law index on the natural frequencies of thick-walled FGM spherical shells are presented. The natural-frequency data for the axial and circumferential mode shapes are obtained. This is a new finding, as the assumed simplification in a sparse matrix causes a numerical truncation error; the natural-frequency values of the presented sparse matrix are much greater than those in a full matrix for thick-walled FGM spherical shells. Full article

The thermal vibrations of a thick-walled functionally graded material (FGM) plate–cylindrical shells in unsteady supersonic flow with a Navier–Stokes equation analytical–numerical flow model and third-order shear deformation theory (TSDT) displacement models are investigated. The aerodynamic pressure load can be provided by using the Navier–Stokes equation analytical–numerical flow model. The data regarding the effect of the aerodynamic pressure load and TSDT model of the motion equation on the thermal stress and displacement of the FGM plate–cylindrical shells in unsteady supersonic flow are calculated with the generalized differential quadrature (GDQ) method. The Navier–Stokes equation analytical–numerical flow model, TSDT model, and advanced shear correction coefficient provide an additional effect on the values of displacement and stress. Full article

A support vector machine based on AdaBoost algorithm (SVM-AB) is proposed for complicated underground mine tunnel modeling. This method accurately predicts the nonlinear propagation characteristics of electromagnetic waves in complex environments in the case of small samples. Firstly, an electromagnetic wave propagation loss model is established by analyzing complex factors including tunnel geometry, wall roughness, tilt, dielectric properties, and multipath effects. Secondly, the complex factors and measured signal strength serve as inputs of the SVM model to establish a nonlinear mapping for preliminary prediction. Furthermore, the AdaBoost algorithm is applied to dynamically correct the SVM prediction errors, further enhancing accuracy. Finally, the measured experiments are carried out in complex underground mine tunnels to verify the proposed theoretical model. The experimental results demonstrate that the proposed SVM-AB model achieves a fitting accuracy of over 99.92%. In addition, compared with the traditional support vector machine, its Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) are reduced by about 84.76% and 92.61%, respectively. The proposed tunnel model has important application value for optimizing the layout of communication system of underground mine tunnel. Full article

Background: To assess longitudinal changes in the in vivo confocal microscopy (IVCM) features during Acanthamoeba keratitis (AK) treatment and develop a prognostic model. Methods: This retrospective study included 59 AK patients who underwent IVCM at baseline and 1 and 3 months. Fourteen morphological features covering pathogen-related characteristics, cyst arrangement patterns, and inflammatory markers were compared between good and poor prognosis groups, which were defined based on clinical outcomes including corneal perforation, the need for therapeutic keratoplasty, or final best-corrected visual acuity (BCVA) ≤ 0.05. Prognostic modeling was performed exclusively using baseline IVCM features and applied univariable and Firth-corrected multivariable logistic regression with collinearity assessment and clinical filtering, followed by 5-fold cross-validation. Results: Among 59 AK patients, 45 (76.3%) had a good prognosis and 14 (23.7%) had a poor prognosis. Poor prognosis eyes showed a higher prevalence of double-walled cysts, trophozoites, and clustered cysts, along with higher cyst density and deeper stromal invasion. In contrast, good-prognosis eyes had more target-like cysts, immature dendritic cells, and mature dendritic cells. Clustered cysts independently predicted poor prognosis (OR = 2.98), whereas target-like cysts (OR = 0.26) and mature dendritic cells (OR = 0.37) were protective (AUC = 0.883; all p < 0.05). Conclusions: IVCM provides a quantitative tool for early outcome prediction and individualized management. Higher cyst burden, clustered cysts, and persistent stromal involvement indicated poorer prognosis, whereas target-like cysts and mature dendritic cells indicated better prognosis. Full article

Surface collisions at Pyrex walls limit the spin coherence in nuclear magnetic resonance gyroscopes (NMRG) vapor cells, while the cavity–stem junction introduces geometry dependent exchange that perturbs the transverse spin relaxation time $T_2$ of ¹²⁹Xe atoms. We combine $T_2$ measurements with Monte Carlo simulations of confined diffusion and surface collisions to decompose the relaxation of Xe atoms and derive a cavity–stem geometry correction for wall relaxation. A structural coupling factor (SCF) is introduced to compress stem length and aperture diameter into a dimensionless metric for diffusion-limited mixing, enabling prediction of the transverse relaxation rate versus geometry. Across eight simulated configurations, the model yields $R^2=0.982$ and agrees with experiments within 7–$9\%$, comparable to the measurement uncertainty ($\pm 0.015{\mathrm{s}}^{-1}$). Using the validated framework, geometry optimization reduces the relaxation rate from $0.225$ to $0.131{\mathrm{s}}^{-1}$ (a $41.8\%$ improvement). This Pyrex surface-collisional analysis provides an in-situ, $T_2$-based route to compare effective surface depolarization across fabrication and surface-treatment protocols while accounting for cavity–stem coupling. Full article

To fill hydrogen fuel cell vehicles quickly and safely, the SAE J2601 protocol has published the MC method, which includes control of the filling speed and pressure target. The filling speed depends on the final filling time, the formula for which is obtained by fitting simulated data. The pressure target depends on the final hydrogen temperature, whose analytical solution is derived from a thermodynamic tank model. This article derives new analytical solutions of the final filling time and hydrogen temperature based on an established lumped-parameter model of the storage tank. Based on the original MC method’s control logic, a new filling method that directly uses the analytical solutions of the final filling time and hydrogen temperature was proposed. The simulation results of the new filling method and the validated model (zone-dimensional gas and a one-dimensional tank wall, 0D1D) are compared. Under the ambient temperature conditions of the 0–20 °C and precooling temperature conditions of −20–0 °C set in this article, results show that the new filling method achieves maximum errors of 4.3 °C in its final hydrogen temperature and 0.9% in a state of charge (SOC) compared to the 0D1D model. Parameter sensitivity analysis reveals that initial pressure has the most significant impact on computational accuracy, followed by ambient and precooling temperatures. Future work may further improve prediction accuracy by incorporating correction factors for initial pressure and ambient temperature. Moreover, since the analytical solution of the final hydrogen temperature inherently includes the precooling temperature parameter, the new filling method can automatically adapt to precooling temperature variations. Full article

The main aim of this study was to evaluate the applicability of a low-cost, double-wall gas metal arc welding (GMAW)-based wire arc additive manufacturing (WAAM) process for aluminum alloy AlMg5, with an emphasis on microstructural heterogeneity, layer-dependent defect formation, and their implications for mechanical performance and geometric characteristics. A Taguchi L9 (3³) design of experiments was employed to investigate the influence of welding current (40–60 A), shielding gas flow (10–20 L/min), and arc correction (0–40%) on wall geometry, material utilization, and overall process quality through multi-response optimization. The optimal parameter set (60 A, 15 L/min, 0% arc correction) resulted in a 54.9% improvement in the Grey Relational Grade compared to the lowest-performing configuration. Metallographic analysis revealed heterogeneous grain evolution governed by the multilayer thermal history, with porosity levels ranging from 3.20% to 3.49% and lack-of-fusion defects preferentially concentrated in interlayer and mid-height regions. The fabricated high-wall structure exhibited hardness values between 72 and 85 HV and an average ultimate tensile strength of 175 MPa. The observed mechanical scatter was consistent with localized microstructural heterogeneity and spatial defect distribution. The results demonstrate that geometric evaluation alone is insufficient as a quality metric for WAAM components and must be complemented by metallographic integrity assessment. Overall, the study highlights the importance of direct parameter optimization in double-wall WAAM structures to mitigate defect formation and enhance mechanical reliability under industrially accessible deposition conditions. Full article