Gabriel Valter Turturica, Bogdan Temelie, Violeta Iancu
Abstract Precise evaluation of a gamma-ray’s interaction position in scintillator detectors is important for their application in medical and industrial imaging. Two approaches can be pursued in achieving this goal: pixelated detectors or monolithic detectors coupled to pixelated readouts. Here, we present the design of a thin monolithic position-sensitive detector for low-energy gamma-rays. Two distinct position-evaluation methods were developed and assessed in terms of accuracy, precision, and imaging capabilities. An analytical model based on a curve-fitting procedure established a performance baseline. A neural network model showed superior performance, offering notable improvements in both accuracy and precision. Qualitative evaluation of the imaging results provided insights into the inherent advantages and limitations of both models. The results demonstrate the ability of a thin monolithic scintillator detector to generate images that significantly surpass the resolution of the readout array for low-energy gamma-ray imaging.
Arash Shams Taleghani, Saeid Yektaei, Vahid Esfahanian
et al.
The vertical tail plays a crucial role in aircraft directional stability and lateral control, especially during low-speed operations such as takeoff and landing. This study examines the effect of aircraft mass on vertical tail geometry through a statistical analysis of 65 design parameters from civil jet aircraft. Aerodynamic performance of a sub-scale Boeing 777-200 vertical tail model was further investigated in a low-speed wind tunnel under rudder deflections and sideslip angles. Experiments were conducted at freestream speeds of 20 and 30 m/s, corresponding to Reynolds numbers of 5 × 10<sup>5</sup> and 7.5 × 10<sup>5</sup>, with model blockage ratios below 2% in all configurations. Side force and drag coefficients were measured for rudder deflections from −30° to +30° and sideslip angles from −7.5° to +7.5°. Results show a nearly linear variation of side force with rudder deflection, while drag exhibits noticeable nonlinearity at higher deflections. At zero sideslip, increasing rudder deflection from 0° to 30° raised the side force coefficient from 0 to 0.65, with a maximum uncertainty of ±0.011, while drag coefficient uncertainty remained below ±0.0055. Furthermore, the application of positive or negative sideslip resulted in substantial variations in the side force coefficient, reaching values of up to ±1.1 depending on the direction. By integrating experimental data with statistical analysis of real aircraft geometries, this study provides reliable quantitative benchmarks and highlights the vertical tail’s aerodynamic importance.
Thermodynamics, Descriptive and experimental mechanics
<b>Background/Objectives</b>: Calcific aortic valve disease (CAVD) is a progressive condition marked by thickening and calcification of the valve leaflets, leading to impaired cardiac function and increased cardiovascular risk. As disease progression is strongly influenced by hemodynamics and lipid accumulation, computational modeling provides a powerful tool for understanding the biomechanical drivers of calcification. <b>Methods:</b> This study investigates the effects of coronary artery flow and varying left ventricular outflow tract (LVOT) velocity profiles on low density lipoprotein (LDL) accumulation and associated aortic valve calcification using a partitioned fluid–structure interaction framework coupled with scalar transport modeling, with a focus on understanding the differential behaviors of the three valve leaflets: the non-coronary cusp (NCC), right coronary cusp (RCC), and left coronary cusp (LCC). Four distinct LVOT flow velocity profiles (anterior, lateral, posterior, and medial) and coronary flow are simulated to determine their effects on the distribution of LDL accumulation and associated calcification across the valve leaflets. <b>Results/Conclusions:</b> Our results indicate that the RCC experiences greatest excursion and lowest calcification. The LCC shows lowest excursion and slightly higher susceptibility for calcification. Finally, the NCC experiences intermediate excursion, but is most prone to calcification.
Mechanics of engineering. Applied mechanics, Descriptive and experimental mechanics
Abstract Thin‐film deposition of fluids is ubiquitous in a wide range of engineering and biological applications, such as surface coating, polymer processing, and biomedical device fabrication. While the thin viscous film deposition in Newtonian fluids has been extensively investigated, the deposition dynamics in frequently encountered non‐Newtonian complex fluids remain elusive, with respect to predictive scaling laws for the film thickness. Here, we investigate the deposition of thin films of shear‐thinning viscoelastic fluids by the motion of a long bubble translating in a circular capillary tube. Considering the weakly elastic regime with a shear‐thinning viscosity, we provide a quantitative measurement of the film thickness with systematic experiments. We further harness the recently developed hydrodynamic lubrication theory to quantitatively rationalize our experimental observations considering the effective capillary number Cae and the effective Weissenberg number Wie, which describe the shear‐thinning and the viscoelastic effects on the film formation, respectively. The obtained scaling law agrees reasonably well with the experimentally measured film thickness for all test fluids. Our work may potentially advance the fundamental understanding of the thin‐film deposition in a confined geometry and provide valuable engineering guidance for processes that incorporate thin‐film flows and non‐Newtonian fluids.
This paper introduces innovative approaches to enhance and develop one-equation RANS models using gene-expression programming. Two distinct strategies are explored: overcoming the limitations of the Boussinesq hypothesis and formulating a novel one-equation turbulence model that can accurately predict a wide range of turbulent wall-bounded flows. A comparative analysis of these strategies highlights their potential for advancing RANS modeling capabilities. The study employs a single-case CFD-driven machine learning framework, demonstrating that machine-informed models significantly improve predictive accuracy, especially when baseline RANS predictions diverge from established benchmarks. Using existing training data, symbolic regression provides valuable insights into the underlying physics by eliminating ineffective strategies. This highlights the broader significance of machine learning beyond developing turbulence closures for specific cases.
Thermodynamics, Descriptive and experimental mechanics
Ediguer Enrique Franco, Sebastián Henao Santa, John Jairo Cabrera
et al.
This work demonstrates the use of an ultrasonic methodology to monitor bubble density in a water column. A flow regime with droplet size distribution between 0.2 and 2 mm was studied. This range is of particular interest because it frequently appears in industrial flows. Ultrasound is typically used when the size of the bubbles is much larger than the wavelength (low frequency limit). In this study, the radius of the bubbles ranges between 0.6 and 6.8 times the wavelength, where wave propagation becomes a complex phenomenon, making existing analytical methods difficult to apply. Measurements in transmission–reception mode with ultrasonic transducers operating at frequencies of 2.25 and 5.0 MHz were carried out for different superficial velocities. The results showed that a time-averaging scheme is necessary and that wave parameters such as propagation velocity and the slope of the phase spectrum are related to the number of bubbles in the column. The proposed methodology has the potential for application in industrial environments.
Thermodynamics, Descriptive and experimental mechanics
As task-based language teaching focuses on real word tasks and the learners need to complete these tasks in the process of learning a foreign or second language, it helps target language fluency and student confidence. That is why second and foreign language teachers and researchers have shown interest in TBLT. This study attempts to investigate the effects of employing task-based writing instruction on Iranian EFL learners’ writing competence. The participants included 69 Iranian EFL learners at the intermediate level and they were placed randomly into a control group and an experimental group. The students in the experimental group performed writing tasks using task-based language teaching techniques, while those in the control group practiced writing skills using traditional writing exercises. To collect the pre-test and post-test data, the researchers administered the writing sections of two paper-based TOEFL tests and analyzed the data through Statistical Package for Social Sciences using descriptive statistics, t-test, and analysis of variance. The results showed significant improvements in the writing ability of the Iranian EFL learners who practiced writing skills using task-based language teaching techniques. Besides, using task-based writing techniques improved the Iranian EFL learners’ ability significantly in terms of different aspects of the writing competence, including sentence mechanics, language use, vocabulary, content, and organization.
In this paper, three controllers including OFCHA (optimal fuzzy control using hedge algebras-HAs), FCHA (fuzzy control using HAs) and CFC (conventional fuzzy control) are designed. Our attention is paid to the stability in the vertical position of a damped-elastic-jointed inverted pendulum subjected to a time-periodic follower force. Different values of the pendulum length are considered. Simulation results are exposed to illustrate the effect of OFCHA in comparison with FCHA and CFC.
Mechanical engineering and machinery, Descriptive and experimental mechanics
We developed the nonlinear model of pipeline dynamics with high-speed liquid motion. On the basis of the variational methods we constructed the nonlinear discrete model and numerical algorithm for investigation of problems of dynamics and dynamical stability of pipeline. We considered examples of dynamical behavior of the system for different velocities of liquid flowing, including the case of critical velocity of flow, when loss of straight line stability of pipeline is possible.
Mechanical engineering and machinery, Descriptive and experimental mechanics