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  • Open Access

    ARTICLE

    Analytical Modeling of Internal Thermal Mass: Transient Heat Conduction in a Sphere under Constant, Exponential, and Periodic Ambient Temperatures

    Liangjian Lei1,2, Yihang Lu1,2,*

    Frontiers in Heat and Mass Transfer, Vol.23, No.6, pp. 2109-2126, 2025, DOI:10.32604/fhmt.2025.072643 - 31 December 2025

    Abstract Internal thermal mass, such as furniture and partitions, plays a crucial role in enhancing building energy efficiency and indoor thermal comfort by passively regulating temperature fluctuations. However, the irregular geometry of these elements poses a significant challenge for accurate modeling in building energy simulations. This study addresses this gap by developing a rigorous analytical model that idealizes internal thermal mass as a sphere, thereby capturing multi-directional heat conduction effects that are neglected in simpler one-dimensional slab models. The transient heat conduction within the sphere is solved analytically using Duhamel’s theorem for three representative indoor air… More >

  • Open Access

    ARTICLE

    Calculation of Commutation Failure Overvoltage in High-Voltage Direct Current Transmission Terminal Systems with Grid-Forming Renewable Energy Sources

    Weibing Xu1, Bo Yao2,*, Xiangjun Quan3, Xunyou Zhang1, Ning Zou2, Shuo Liu2, Jia Wang4, Jiansuo Zhang4

    Energy Engineering, Vol.122, No.10, pp. 4225-4243, 2025, DOI:10.32604/ee.2025.066738 - 30 September 2025

    Abstract The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia. Grid-forming renewable energy sources (GF-RES) has a significant improvement effect on system inertia. Commutation failure faults may cause a short-term reactive power surplus at the sending end and trigger transient overvoltage, threatening the safe and stable operation of the power grid. However, there is a lack of research on the calculation method of transient overvoltage caused by commutation failure in high-voltage DC transmission systems with grid-forming renewable energy sources integration. Based on the existing equivalent model of high-voltage… More >

  • Open Access

    PROCEEDINGS

    Thermoelastic Transient Memory Response Analysis of Spatio-Temporal Non-Localized Porous Hollow Cylinder Based on Moore-Gibson-Thompson Thermoelasticity Theory

    Yixin Zhang, Yongbin Ma*

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.33, No.1, pp. 1-1, 2025, DOI:10.32604/icces.2025.012268

    Abstract In this paper, a novel porous thermoelastic model is developed, building upon the existing framework of thermoelastic model. The objective of this study is to investigate the thermoelastic response behavior of porous materials. The Klein-Gordon (KG) operator is employed to describe the effect of spatio-temporal non-localization in the constitutive equation, and the memory-dependent derivative (MDD) is incorporated into the Moore-Gibson-Thompson (MGT) heat conduction equation. The model is applied to study the thermoelastic response of hollow porous cylinders under thermal shock, which accurately captures the complex micro-interaction characteristics and memory-dependent properties of the porous structure. Subsequently,… More >

  • Open Access

    PROCEEDINGS

    Improved Frequency Modulation Method Based on Sphere-String Mechanical Antenna

    Xinyan Yao, Weifeng Yuan*

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.33, No.1, pp. 1-3, 2025, DOI:10.32604/icces.2025.011474

    Abstract In addressing the challenging problems of underwater communication, mechanical antenna (MA) provides a new direction for greatly reducing the size of low frequency communication equipment and breaking through the Chu-Harrington limit [1,2]. MA refers to the generation of low-frequency electromagnetic waves by mechanically driving materials with strong electric or magnetic fields. This direction has attracted many researchers from fields such as materials, mechanics, and mechanics to conduct research. Various forms of MA currently exist, but research on their modulation methods remains limited. The modulation methods of MA primarily include amplitude modulation, frequency modulation, and phase More >

  • Open Access

    ARTICLE

    Relevant Fluid Dynamics Aspects of the Internal Ballistics in a Small-Scale Hybrid Thruster

    Sergio Cassese1, Riccardo Guida2,3,*, Daniele Trincone1, Stefano Mungiguerra1, Raffaele Savino1

    FDMP-Fluid Dynamics & Materials Processing, Vol.21, No.6, pp. 1299-1337, 2025, DOI:10.32604/fdmp.2025.065605 - 30 June 2025

    Abstract Robust numerical tools are essential for enabling the use of hybrid rocket engines (HREs) in future space applications. In this context, Computational Fluid Dynamics (CFD) transient simulations can be employed to analyse and predict relevant fluid dynamics phenomena within the thrust chamber of small-scale HREs. This work applies such techniques to investigate two unexpected behaviours observed in a 10 N-class hydrogen peroxide-based hybrid thruster: an uneven regression rate during High-Density Polyethylene (HDPE) and Acrylonitrile Butadiene Styrene (ABS) fuel tests, and non-negligible axial consumption in the ABS test case. The present study seeks to identify their… More >

  • Open Access

    ARTICLE

    Transient Stability Assessment Model and Its Updating Based on Dual-Tower Transformer

    Nan Li1,2,*, Jingxiong Dong2, Liang Tao3, Liang Huang3

    Energy Engineering, Vol.122, No.7, pp. 2957-2975, 2025, DOI:10.32604/ee.2025.062667 - 27 June 2025

    Abstract With the continuous expansion and increasing complexity of power system scales, the binary classification for transient stability assessment in power systems can no longer meet the safety requirements of power system control and regulation. Therefore, this paper proposes a multi-class transient stability assessment model based on an improved Transformer. The model is designed with a dual-tower encoder structure: one encoder focuses on the time dependency of data, while the other focuses on the dynamic correlations between variables. Feature extraction is conducted from both time and variable perspectives to ensure the completeness of the feature extraction… More > Graphic Abstract

    Transient Stability Assessment Model and Its Updating Based on Dual-Tower Transformer

  • Open Access

    ARTICLE

    Optimization of Guide Vane Geometry in a Pump-as-Turbine through an Orthogonal Test Approach

    Fengxia Shi1,2, Pengcheng Wang1,*, Haonan Zhan1, Xiangyun Shi1

    FDMP-Fluid Dynamics & Materials Processing, Vol.21, No.5, pp. 1221-1238, 2025, DOI:10.32604/fdmp.2025.062244 - 30 May 2025

    Abstract To investigate the impact of guide vane geometry—specifically, outlet angle, blade count, and radial height—on the performance of a Pump as Turbine (PAT), radial guide vanes were introduced upstream of the impeller in an IS80-50-315 low-specific-speed centrifugal PAT. Using an orthogonal test design, numerical simulations were conducted on 16 different PAT configurations, and the influence of vane geometry on performance was analyzed through a range analysis to determine the optimal parameter combinations. The results indicate that the number of guide vane blades significantly affects both the hydraulic efficiency and water head of the PAT under More >

  • Open Access

    ARTICLE

    Transient Multiphase Study on the Influence of Well Trajectory on Horizontal Shale Gas Production

    Anqi Du1,*, Ming Wen2, Jian Yang1

    FDMP-Fluid Dynamics & Materials Processing, Vol.21, No.4, pp. 939-957, 2025, DOI:10.32604/fdmp.2024.058553 - 06 May 2025

    Abstract Horizontal wells play a crucial role in enhancing shale gas reservoir production. This study employs transient multiphase simulation to investigate the impact of well trajectory on production optimization throughout a well’s life cycle. The research uses OLGATM as a simulator to examine six well trajectories: toe-up, toe-down, smooth horizontal, undulated toe-up, undulated toe-down, and undulated horizontal. Initial findings indicate comparable production rates across different trajectories during the early production phase, with toe-up wells showing slightly better performances due to minimal slugging. However, as the reservoir pressure decreases, the well trajectory significantly influences production. Horizontal wells achieve More >

  • Open Access

    ARTICLE

    Analysis of Fluid Flow and Optimization of Tubing Depth in Deep Shale Gas Wells

    Sheng Ju, Jie Liu*

    FDMP-Fluid Dynamics & Materials Processing, Vol.21, No.3, pp. 529-542, 2025, DOI:10.32604/fdmp.2024.057535 - 01 April 2025

    Abstract As shale gas technology has advanced, the horizontal well fracturing model has seen widespread use, leading to substantial improvements in industrial gas output from shale gas wells. Nevertheless, a swift decline in the productivity of individual wells remains a challenge that must be addressed throughout the development process. In this study, gas wells with two different wellbore trajectory structures are considered, and the OLGA software is exploited to perform transient calculations on various tubing depth models. The results can be articulated as follows. In terms of flow patterns: for the deep well A1 (upward-buckled), slug flow… More > Graphic Abstract

    Analysis of Fluid Flow and Optimization of Tubing Depth in Deep Shale Gas Wells

  • Open Access

    ARTICLE

    «Silver Bullet of Acidification»: Studying Anti-PD Neuroprotective Mechanisms of Transient pH-Decrease

    Kristina A. Kritskaya, Evgeniya I. Fedotova, Alexander D. Nadeev*, Alexey V. Berezhnov*

    BIOCELL, Vol.49, No.3, pp. 451-464, 2025, DOI:10.32604/biocell.2025.061624 - 31 March 2025

    Abstract Objective: Activation of mitophagy is a promising option to overcome the mitochondrial malfunction that accompanies many diseases. Herein, we investigate the mechanisms underlying the ability of sodium lactate and pyruvate to initiate mitophagy, from the perspective of action on mitochondrial network and expression levels. Methods: Fluorescent and confocal microscopy was used to assess key cell parameters characterizing the state of the mitochondrial network and the level of mitophagy in human fibroblasts carrying mutations in genes encoding LRRK2 and PINK1 after the combined application of lactate and pyruvate and after direct acidification. qRT-PCR was used to… More >

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