Zhiguang Zhang, Caisheng Wei, Guanhua Huang, Zeyang Yin^*

The International Conference on Computational & Experimental Engineering and Sciences, Vol.33, No.3, pp. 1-1, 2025, DOI:10.32604/icces.2025.010967

Abstract An optimal predictive control method for spacecraft rendezvous based on Koopman operator is proposed for the the libration point rendezvous problem of Earth-moon system. Firstly, the relative motion dynamics model between the chaser and the target spacecraft in the Earth-moon system is established. Secondly, considering the influence of nonlinearity on spacecraft rendezvous control, a global linearization method of nonlinear rendezvous system driven by Koopman operator is proposed. In this method, the Koopman linearization operator is approximated by the extended dynamic mode decomposition (EDMD) method on the finite dimension. Subsequently, based on the linearization model of… More >

Ahmad Faldo¹, Labanta Marbun¹, Hezekiah Lemuel Putra Zebua¹, Fateha Fateha², Rossy Choerun Nissa², Yurin Karunia Apsha Albaina Iasya³, Riri Uswatun Annifah³, Amrul Amrul¹, Yeyen Nurhamiyah^2,*

Journal of Polymer Materials, Vol.42, No.3, pp. 743-755, 2025, DOI:10.32604/jpm.2025.069981 - 30 September 2025

Abstract Conventional bioplastic production from seaweed often relies on extraction processes that are costly, time-consuming, and yield limited product. This study presents a direct fabrication method using Gracilaria sp., a red seaweed rich in polysaccharides, to produce bioplastic films without the need for extraction. Sorbitol was incorporated as a plasticizer at concentrations of 0%–10% (w/w) to modify film characteristics. Thermal analysis revealed improved stability at moderate sorbitol levels (5%–7%), while excessive plasticizer slightly reduced thermal resistance. Mechanical testing showed that sorbitol increased film flexibility and elongation at break, though tensile strength and stiffness declined. Tear strength followed More >

Ruibo Wei^1,2, Yao Kong³, Mengzhao Li^1,2, Feng Liu^1,2,*, Fang Cheng^4,*

CMC-Computers, Materials & Continua, Vol.84, No.1, pp. 1507-1528, 2025, DOI:10.32604/cmc.2025.063722 - 09 June 2025

Abstract To address uncertainties in satellite orbit error prediction, this study proposes a novel ensemble learning-based orbit prediction method specifically designed for the BeiDou navigation satellite system (BDS). Building on ephemeris data and perturbation corrections, two new models are proposed: attention-enhanced BPNN (AEBP) and Transformer-ResNet-BiLSTM (TR-BiLSTM). These models effectively capture both local and global dependencies in satellite orbit data. To further enhance prediction accuracy and stability, the outputs of these two models were integrated using the gradient boosting decision tree (GBDT) ensemble learning method, which was optimized through a grid search. The main contribution of this More >

Pugazhenthi Sivasankar^1,*, Austin B. Probe², Tarek A. Elgohary¹

Digital Engineering and Digital Twin, Vol.2, pp. 169-205, 2024, DOI:10.32604/dedt.2024.052805 - 31 December 2024

Abstract In Space Situational Awareness (SSA), accurate and efficient uncertainty quantification and propagation are essential for various applications, such as conjunction analysis, track correlation, and orbit prediction. The propagation of the probability density function (PDF) in nonlinear systems results in non-Gaussian distributions, which are difficult to approximate. Furthermore, the computational cost of approximating the PDF increases exponentially with the number of random variables, a phenomenon known as the curse of dimensionality. To address these challenges, the Orthogonal Probability Approximation (OPA) method is presented for high-fidelity uncertainty propagation and PDF approximation in nonlinear dynamical systems. The method… More >

Changtao Wang¹, Honghua Dai^1,*

The International Conference on Computational & Experimental Engineering and Sciences, Vol.29, No.3, pp. 1-2, 2024, DOI:10.32604/icces.2024.010943

Abstract Orbital uncertainty propagation is fundamental in space situational awareness-related missions such as orbit prediction and tracking. Linear models and full nonlinear Monte Carlo simulations were primarily used to propagate uncertainties [1]. However, these methods hampered the application due to low precision and intensive computation. Over the past two decades, numerous nonlinear uncertainty propagators have been proposed. Among these methods, the state transition tensor (STT) method has been widely used due to its controllable accuracy and high efficiency [2]. However, this method has two drawbacks. First, its semi-analytical formulation is too intricate to implement, which hinders… More >

Ahmad Ababneh¹, Yousef Sanjalawe², Salam Fraihat^3,*, Salam Al-E’mari⁴, Hamzah Alqudah⁵

CMC-Computers, Materials & Continua, Vol.80, No.1, pp. 1347-1379, 2024, DOI:10.32604/cmc.2024.050600 - 18 July 2024

Abstract This study introduces the Orbit Weighting Scheme (OWS), a novel approach aimed at enhancing the precision and efficiency of Vector Space information retrieval (IR) models, which have traditionally relied on weighting schemes like tf-idf and BM25. These conventional methods often struggle with accurately capturing document relevance, leading to inefficiencies in both retrieval performance and index size management. OWS proposes a dynamic weighting mechanism that evaluates the significance of terms based on their orbital position within the vector space, emphasizing term relationships and distribution patterns overlooked by existing models. Our research focuses on evaluating OWS’s impact… More >

Changtao Wang, Honghua Dai^*, Wenchuan Yang

Digital Engineering and Digital Twin, Vol.1, pp. 3-13, 2023, DOI:10.32604/dedt.2023.044210 - 28 December 2023

Abstract A novel Adaptive Parallel Feedback-Accelerated Picard Iteration (AP-FAPI) method is proposed to meet the requirements of various aerospace missions for fast and accurate orbit propagation. The Parallel Feedback-Accelerated Picard Iteration (P-FAPI) method is an advanced iterative collocation method. With large-step computing and parallel acceleration, the P-FAPI method outperforms the traditional finite-difference-based methods, which require small-step and serial integration to ensure accuracy. Although efficient and accurate, the P-FAPI method suffers extensive trials in tuning method parameters, strongly influencing its performance. To overcome this problem, we propose the AP-FAPI method based on the relationship between the parameters More >

Zipu Yan^1,2, Honghua Dai^1,2,*, Xiaokui Yue^1,2

The International Conference on Computational & Experimental Engineering and Sciences, Vol.26, No.3, pp. 1-1, 2023, DOI:10.32604/icces.2023.09138

Abstract As a significant research interest in orbital mechanics, periodic orbits are fundamental for understanding orbital behaviors and space explorations. Although the harmonic balance (HB) method and its variants have been the most widely-used approaches for periodic dynamical systems, they are seldom applied to celestial dynamics. Here we use the reconstruction harmonic balance (RHB) method for solving periodic orbits. Starting from a presupposed Fourier form and an initial guess at the solution, the algorithm uses timedomain collocation points to optimally reconstruct the high-order HB procedure without complicated symbolic operations and non-physical solutions. Following a description of More >

Medta Boupan^1,2, Kanyapak Prompang¹, Achiraya Chompunuch¹, Piwat Boonma¹, Arthit Neramittagapong^1,2,3,4, Somnuk Theerakulpisut⁵, Sutasinee Neramittagapong^1,2,3,*

Journal of Renewable Materials, Vol.11, No.7, pp. 2985-3000, 2023, DOI:10.32604/jrm.2023.026397 - 05 June 2023

Abstract Isosorbide is a multi-purpose chemical that can be produced from renewable resources. Specifically, it has been investigated as a replacement for toxic bisphenol A (BPA) in the production of polycarbonate (PC). In this study, the synthesis of isosorbide by sorbitol dehydration using a cerium-based catalyst derived from calcined cerium (IV) sulfate (300°C, 400°C, 450°C, 500°C, and 650°C) was investigated. The reaction occurred in a high-pressure reactor containing nitrogen gas. Advanced instrumental techniques were applied to analyze the characteristics of the calcined catalyst. The results showed that the calcined catalysts demonstrated different crystalline structures and sulfate More > Graphic Abstract

Saifur Rahman Sabuj¹, Mohammad Saadman Alam², Majumder Haider², Md Akbar Hossain³, Al-Sakib Khan Pathan^4,*

CMES-Computer Modeling in Engineering & Sciences, Vol.136, No.2, pp. 1053-1089, 2023, DOI:10.32604/cmes.2023.024078 - 06 February 2023

Abstract This paper discusses the significance and prospects of low altitude small satellite aerial vehicles to ensure smooth aerial-ground communications for next-generation broadband networks. To achieve the generic goals of fifthgeneration and beyond wireless networks, the existing aerial network architecture needs to be revisited. The detailed architecture of low altitude aerial networks and the challenges in resource management have been illustrated in this paper. Moreover, we have studied the coordination between promising communication technologies and low altitude aerial networks to provide robust network coverage. We talk about the techniques that can ensure userfriendly control and monitoring More > Graphic Abstract