bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational modelling of mouse atrio ventricular node action potential and automaticity
Authors: Bartolucci Chiara , Mesirca Pietro , Ricci Eugenio , Sales‐Bellés Clara , Torre Eleonora , Louradour Julien , Mangoni Matteo Elia , Severi Stefano 
Published: September 2024

AbstractThe atrioventricular node (AVN) is a crucial component of the cardiac conduction system. Despite its pivotal role in regulating the transmission of electrical signals between atria and ventricles, a comprehensive understanding of the cellular electrophysiological mechanisms governing AVN function has remained elusive. This paper presents a detailed computational model of mouse AVN cell action potential (AP). Our model builds upon previous work and introduces several key refinements, including accurate representation of membrane currents and exchangers, calcium handling, cellular compartmentalization, dynamic update of intracellular ion concentrations, and calcium buffering. We recalibrated and validated the model against existing and unpublished experimental data. In control conditions, our model reproduces the AVN AP experimental features, (e.g. rate = 175 bpm, experimental range [121, 191] bpm). Notably, our study sheds light on the contribution of L‐type calcium currents, through both Cav1.2 and Cav1.3 channels, in AVN cells. The model replicates several experimental observations, including the cessation of firing upon block of Cav1.3 or INa,r current. If block induces a reduction in beating rate of 11%. In summary, this work presents a comprehensive computational model of mouse AVN cell AP, offering a valuable tool for investigating pacemaking mechanisms and simulating the impact of ionic current blockades. By integrating calcium handling and refining formulation of ionic currents, our model advances understanding of this critical component of the cardiac conduction system, providing a platform for future developments in cardiac electrophysiology.
imageKey points
This paper introduces a comprehensive computational model of mouse atrioventricular node (AVN) cell action potentials (APs).
Our model is based on the electrophysiological data from isolated mouse AVN cells and exhibits an action potential and calcium transient that closely match the experimental records.
By simulating the effects of blocking specific ionic currents, the model effectively predicts the roles of L‐type Cav1.2 and Cav1.3 channels, T‐type calcium channels, sodium currents (TTX‐sensitive and TTX‐resistant), and the funny current (If) in AVN pacemaking.
The study also emphasizes the significance of other ionic currents, including IKr, Ito, IKur, in regulating AP characteristics and cycle length in AVN cells.
The model faithfully reproduces the rate dependence of action potentials under pacing, opening the possibility of use in impulse propagation models.
The population‐of‐models approach showed the robustness of this new AP model in simulating a wide spectrum of cellular pacemaking in AVN.
Studies of the Thermalhydraulics Subchannel Code ASSERT-PV 3.2-SC for Supercritical Applications
Authors: Nava-Dominguez Armando , Huang Xianmin , Liu Songyu 
Published: September 2024

Abstract
Over the last decade, several international thermalhydraulics benchmarking efforts have been carried out to support the development of the Generation IV supercritical water-cooled reactor (SCWR) concept. These benchmarking efforts aimed to assess the readiness of computer codes to predict the thermalhydraulics behavior of supercritical fluids for nuclear fuel assembly applications. The results from the benchmarking also shed light on knowledge gaps. Throughout the years, several advancements in this area have been achieved, resulting in relevant conclusions and observations. Furthermore, experimental campaigns have been carried out worldwide to further our knowledge on the thermalhydraulics of supercritical fluids. The nuclear industry uses the subchannel approach to study the thermalhydraulics behavior of nuclear fuel assemblies in detail. In Canada, the subchannel code advanced solution of subchannel equations in reactor thermalhydraulics—pressure velocity (ASSERT-PV) is the qualified code for subchannel applications. ASSERT-PV was modified to handle supercritical conditions, resulting in an interim code version. This publication presents relevant subchannel analyses using the interim supercritical version of ASSERT-PV for fuel assemblies cooled with supercritical fluids.
Study of the Mechanism of Perceived Rotational Acceleration of a Bionic Semicircular Canal on the Basis of the “Circular Geometry Hypothesis”
Authors: Bian Yixiang , Liu Wujie , Dai Junjie , Wen Xianhua , Jiang Yani 
Published: September 2024

Abstract
Academia often uses the “circular geometry hypothesis” to explain the sensing principle of the human semicircular canal (SCC) system for angular acceleration, which is widely accepted as an important angular acceleration sensor in the human balance system. On the basis of this hypothesis and the anatomical structure of human SCCs, a series of physical SCC models with different geometries at 4× magnification were prepared via three-dimensional printing and modification of hydrogels. Theoretical models of the SCC perception mechanism were established. Then, impulse angular acceleration, sinusoidal rotation, and sinusoidal linear stimulation were applied to the models, and their responses were visually observed and analyzed in detail. As a result, the circular SCC model had a larger system gain and a smaller phase difference for angular acceleration stimulation but a smaller system gain and a larger phase difference for linear acceleration stimulation. These results verified that the circular semicircular canal was more sensitive to angular acceleration. Our bionic model is hoped to be used for demonstrating the human SCC working process, facilitating researchers in better understanding of the working mechanism of the human SCC, or as a manual model for medical staff to simulate the diagnosis and treatment of human SCC.
Influences of Tooth Crack on Dynamic Characteristics of a Multi-Stage Gear Transmission System Considering the Flash Temperature
Authors: Zhang Xu , Li Qiu , Li Hongwei 
Published: September 2024

Abstract
The crack failure is prone to happen for the gear teeth under alternating loads. The crack reduces the time-varying meshing stiffness, thus causing changes in the system vibration responses. Moreover, the tooth friction leads to the flash temperature on the tooth surface, and the flash temperature causes the deformation of the tooth profile. The flash temperature stiffness generated by this deformation is an important component of the resultant meshing stiffness, and inevitably influences the dynamic characteristics. Hence, this paper makes an effort to provide a clear understanding of the relationship between the tooth crack and nonlinear dynamics for a multistage gear transmission system considering the flash temperature in a mixed friction state. The time-varying meshing stiffness and flash temperature stiffness are separately calculated using the potential energy method and Hertz's theory, and the torsional dynamic model is established by the lumped mass method for the system with high-speed driving gear crack in the mixed friction state. The influences of the flash temperature and crack on the dynamic behaviors are studied through a bifurcation diagram, frequency spectrum, phase portrait, and Poincare map, and the frequency spectra of numerical simulation and experimental testing are compared. The results indicate that both flash temperature and tooth crack decrease the time-varying meshing stiffness, the flash temperature increases the displacement amplitude of chaotic motion, and the tooth crack enlarges the interval of chaotic motion. Meanwhile, the results provide a suitable meshing frequency, which puts the system in a stable working state. The research provides significant guidance for monitoring the crack fault of multistage gear transmission systems.
Navigating Technological Risks: An Uncertainty Analysis of Powertrain Technology in Hybrid-Electric Commuter Aircraft
Authors: Diamantidou Dimitra-Eirini , Soibam Jerol , Zaccaria Valentina , Kalfas Anestis I. 
Published: September 2024

Abstract
This study addresses the uncertainties in hybrid-electric powertrain technology for a 19-passenger commuter aircraft, focusing on two future Entry-Into-Service timeframes: 2030 and 2040. The methodology is split into a preliminary optimization of aircraft design based on nominal technology scenarios followed by Monte Carlo simulations to investigate the impact of diverse technology projections and distribution types. Advanced surrogate modeling techniques, leveraging deep neural networks (DNN) trained on a dataset from an aircraft design framework, are employed. Key outcomes from this work reveal a marked increase in computational efficiency, with a speed-up factor of approximately 500 times when utilizing surrogate models. The results indicate that the 2040 entry-into-service (EIS) scenario could achieve larger reductions in fuel and total energy consumption—20.4% and 15.8% respectively—relative to the 2030 scenario, but with higher uncertainty. Across all scenarios examined, the hybrid-electric model showcased superior performance compared to its conventional counterpart. The battery-specific energy density is proved to be a critical parameter of the aircraft’s performance across both timeframes. The findings emphasize the importance of continuous innovation in battery and motor technologies to target toward greater system-level efficiency and reduced environmental impact.
Aerodynamic Feasibility Investigation of the Novel Experimental Rig on Turbine Blade Tip With High Relative Motion
Authors: Peng X. , Jiang H. , Lu S. , Zhang Z. 
Published: September 2024

Abstract
The relative casing motion can significantly alter the over-tip-leakage (OTL) flow aerodynamic performances. Traditional tip experimental facilities for relative motion researches, including stationary linear cascade with low-speed moving belt, annular cascade with rotating outer wall, and full-scale experimental rig with rotating blade, were either extremely costly or not capable to reproduce engine-representative casing Mach number. Very recently, a novel design concept for high-speed disk rotor rig has been proposed for tip research. Subsequent to this research, the present study evaluates the aerodynamic performances and the periodicity of the disk rotor rig design using Reynolds-averaged Navier–Stokes computational fluid dynamics simulation. Furthermore, first-of-its-kind experimental results of total pressure loss distributions measured by five-hole probe under high relative casing Mach number are reported. The results demonstrate the applicability of the disk rotor experimental rig for tip aerodynamic investigations.
Investigation of Flame Response in a Swirling Micromix Hydrogen–Methane Combustor
Authors: Liu Dewen , Feng Zhenzhen , Tian Xiaojing , Xu Liangliang , Gu Mingming , Lin Yang , Xia Xi , Qi Fei 
Published: September 2024

Abstract
Hydrogen-enriched natural gas combustion is a hot topic in industrial and academic communities due to the need for carbon emission reduction. However, thermoacoustic instability poses a major challenge for lean combustion development, particularly the higher frequency combustion oscillations. This study investigates the flame response in micromix hydrogen/methane flames within a low to medium frequency range of 50–1200 Hz, revealing a critical mixing ratio. Above this threshold, the flame response is dominated by hydrogen combustion, whereas below it, methane combustion takes precedence. Overall speaking, the hydrogen addition significantly enlarges the low-pass filter limit of the flame transfer function (FTF). Simultaneous OH* chemiluminescence and particle image velocimetry (PIV) experiments demonstrate that the gain is associated with the flame size and the number of acoustic-induced vortices on the flame surface. Higher frequency acoustic forcing leads to flame responses out of phase at different longitudinal positions, resulting in a low global flame response. Hydrogen addition reduces the flame length and enhances the FTF gain at specific frequencies.
Numerical Study of Low Engine Order Excitations Due to Manufacturing Variability Part II: An Efficient Approach for Stochastic Studies
Authors: Gallardo Juan Manuel , Escobar Óscar Pérez 
Published: September 2024

Abstract
In turbomachinery rows, the geometric variability between the airfoils induces nonuniformity in the flow, which directly translates into low engine order (LEO) excitation and vibration in the adjacent rows. Direct simulations of this phenomenon involve full-row computational fluid dynamics (CFD) analyses, where the exact geometry of each individual blade needs to be properly reproduced. The related computational cost of such simulations is very significant. Since the geometric variability due to the manufacturing scatter is stochastic, valuable information could be derived from Monte Carlo analyses involving randomly generated geometries; nevertheless, this approach would be very resource-intensive. In this paper, we propose a simplified method to determine the flow perturbation generated by this geometric variability. The method is based on studying the underlying properties of the geometric scatter using principal component analysis (PCA) techniques, obtaining a compact description of the variability of the airfoils. The flow perturbation due to a reduced number of reference cases is obtained through direct, large scale simulations. By assuming linearity in the flow perturbations, the solution for a general case of geometric distortion may be obtained very efficiently from these reference cases, which makes Monte Carlo studies to analyze stochastic geometric distortion easily affordable. The capabilities of the method are demonstrated in a test case considering the real geometry scatter from an aircraft turbine. According to the results, the average LEO response due to the random geometry scatter involves significant vibration levels, comparable (in terms of alternating stress) to the response due to the blade-passing excitation.
Dynamic Response of a Rotor Supported on Hybrid Bearings in Air, Water, and Liquid Nitrogen: Measurements and Comparisons to Predictions
Authors: Yi Howon , Kim Kyuman , Jung Hyunsung , Ryu Keun 
Published: September 2024

Abstract
Modern liquid rocket engine turbopumps implement hybrid bearings, which combine hydrostatic and hydrodynamic fluid film principles, in compact and lightweight units known for their superior reusability, durability, and reliability. This study aims to provide extensive and reliable test data for the purpose of anchoring and benchmarking predictive tools for these bearings. This paper provides comprehensive dynamic response measurements of a rotor weighing 10.40 kg and approximately 60 mm in diameter at the bearing locations. The test rotor is supported on two hybrid journal bearings with a bearing length to bearing diameter ratio of approximately 0.42 and a bearing radial clearance to rotor radius ratio of around 0.0017. The bearings are tested with air, water, and liquid nitrogen, serving as surrogate test fluids for common propellants in liquid rocket engines. Rotor run-up and speed coast-down tests are conducted to measure shaft motion responses. The results clearly demonstrate that the rotordynamic characteristics of the test rotor supported on the hybrid journal bearings largely rely on properties of the test fluids and their feeding conditions. Notably, when air is pressurized into the test bearings, the shaft motion responses differ markedly from those observed with water and liquid nitrogen, primarily due to significantly lower stiffness and damping coefficients. Furthermore, rotor speed coast-down tests for each test fluid exhibit notable differences in coast-down speed over time characteristics, depending on the test fluid properties. The predicted rotor imbalance responses exhibit excellent correlation with the measurement data. The steady increase of demand and growth of the fluid film bearing technology for reusable rocket engines require accurate bearing design tools, the extensive component testing, and the implementation of the technology. The validated and developed bearing predictive models from previous research demonstrate well the characteristics of bearings under various operating fluids conditions. The findings and database presented in this work contribute not only to comprehending the performance of hybrid bearings but also to understanding and enhancing the dynamic characteristics of rotor systems supported on hybrid bearings.
Isothermal Flow Field Characterization of a Full-Scale Sector Combustor at Elevated Pressures
Authors: Rathod Darshan D. , Kumar Sonu , Chaudhuri Swetaprovo , Panda Pratikash , Basu Saptarshi 
Published: September 2024

Abstract
An experimental investigation in a sector (20 deg) of full-scale annular gas turbine combustor is performed. The sector combustor is optically accessible for the flow and flame visualization of the primary and exit zones of the combustor. The distinctive feature of the experimental setup is that it preserves the geometrical details of an annular combustor that includes the casing, dome and combustor liner. The combustor design features a series of primary and secondary dilution holes with multiple film cooling strips on the outer and inner liner. In the present study, the combustor is operated at inlet Mach numbers of 0.02–0.3 at operating absolute pressures of 1–5 bar. Static pressure measurements are performed at multiple locations in the rig to characterize the pressure drop across the combustor. Two-dimensional particle image velocimetry (PIV) is performed to measure the velocity fields of the primary and exit zones of the combustor simultaneously. The results show the presence of a central recirculation zone (CRZ), high-velocity annular jets, and a pair of dilution jets in the primary zone of the combustor. The steady-state flow structures are invariant of inlet Mach number and pressures. The relationship between the relative pressure drop across the combustor and the combustor inlet condition is obtained. Mass flowrate and momentum flux are calculated for the flow through the swirler, central recirculation zone, the primary dilution jets, and the exit zone. The paper shows how the flow structures in a realistic combustor change with variations in global combustor parameters.
Development of a Virtual Chemistry Reaction Mechanism for H2/CH4 Turbulent Combustion Modelling
Authors: Castellani S. , Andreini A. , Meloni R. 
Published: September 2024

Abstract
The identification of the combustion model is always guided by the compromise between accuracy and computational cost. While species transport models offer accuracy, their computational cost requirement can become prohibitive, especially when de-aling with higher-order hydrocarbon fuels. To mitigate this, the virtual mechanism definition aims to optimize the predictivity minimizing the amount of information to be transported. Thereby the virtual mechanism leverages fictitious species and a few step reactions whose parameters calibration is performed with a genetic algorithm. This work outlines the procedure for the derivation of a virtual reaction mechanism for the study of lean H2/CH4 fuel mixtures with 60% of H2 content (by vol.). These conditions require an adequate characterization of the virtual species differential diffusion oriented to reconstruct the flame sensitivity toward the aerodynamic stretch. After the mechanism derivation, its predictivity has been validated on a swirl-stabilized perfectly premixed turbulent test case. The artificially thickened flame model has been adopted to allow the flame front discretization on an large eddy simulation (LES) grid and to model the turbulence chemistry interaction. The numerical results show a very good agreement with the experimental optical measurements confirming the effectiveness of this approach for predicting the H2/CH4 blend.
Modeling of Ball Screw–Nut Interface Stiffness With Wear (Ball Screw Wear Dynamics)
Authors: Heydarnia Hoda , Altintas Yusuf 
Published: September 2024

Abstract
The effects of wear, preload loss, and missing balls on the dynamics of ball screw drives in machine tools are modeled and incorporated into the finite element model of the drive assembly for condition monitoring. The contacts between the ball–nut and ball–screw are modeled using Hertzian springs, whose stiffnesses vary as a function of the worn contact area. These contact stiffnesses are then transformed to the finite element nodes on the nut and screw. The frequency response functions at the motor shaft and table, which can be measured by commercial computer numerical control (CNC), are predicted for various faults at different positions of the table. The experimentally validated model demonstrates that the faults primarily affect the first coupled torsional-axial mode of the ball screw drive and can be utilized for automated condition monitoring of ball screw drives.
Hyperspectral Analysis of Silicon Nanowires Manufactured Through Metal-Assisted Chemical Etching
Authors: Lee Pee-Yew , Lu Guo-Hao , Bai Yi-Hong , Chen Cheng-You , Wu Li-Yan , Weng Chun-Jen , Huang Hung Ji , Lin Yung-Sheng 
Published: September 2024

Abstract
This study used hyperspectral imaging to analyze localized near-field interactions between incident electromagnetic waves and silicon nanowire (SiNW) arrays manufactured through catalytic etching of Si wafers for different durations. The results revealed that the unetched upper surface area on Si wafers and reflection of incident light decreased with increasing etching time. A light reflection band peaking at approximately 880 nm was generated from arrays etched for more than 1 h. We used six separate hyperspectral images to analyze the wavelength-dependent spatial optical responses of the fabricated SiNW arrays. The images revealed hot spots of light reflection from unetched Si surfaces in the wavelength range of 470–750 nm and a resonant peak at 880 nm for a photonic crystal derived from a random SiNW array. Accordingly, hyperspectral imaging enables the assessment of localized optical responses of SiNW arrays, which can then be optimized to cater to various applications.
Local Conjugate Meshing Performance Analysis of an Enveloping Hourglass Worm Drive Based on Medium Gear
Authors: Li Zhongtao , Chen Yonghong , Wang Xinhua , Luo Wenjun , Chen Bingkui 
Published: September 2024

Abstract
Due to the low error sensitivity, the local conjugate enveloping hourglass worm drive based on medium gear is being intensively investigated, and this article examines the local conjugate meshing performance of such a worm drive. In this article, the local conjugate principle grounded in modified involute is proposed, and the local conjugate meshing hourglass worm drive using this approach is established; the boundary conditions of the modified involute are set up, and the oblique planar gear is converted to modified involute gear form; the meshing contact area of the worm drive is analyzed using tooth contact analysis (TCA), and finite element analysis (FEA) is executed to validate TCA's accuracy and perform loaded tooth contact analysis (LTCA); the mathematical models of the micro meshing properties are derived, and the effects of the modification position and range on meshing performance are examined. The findings indicate that the modification parameters influence the transmission pair's meshing performance, which subsequently affects the transmission performance. Thus, by reasonably selecting the modification position and range, a local conjugate hourglass worm drive with better meshing performance can be obtained.