Journal of Science and Transport Technology

Analytical study on nonlinear buckling of spiral-stiffened FG-CNTRC toroidal shells segments with piezoelectric layers and generalized curvature under external pressure

Do Thi Kieu My, Kieu Lan Huong, Nguyen Van Tien — Sat, 27 Dec 2025 00:00:00 +0000

This paper presents an analytical investigation into the nonlinear stability of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) toroidal shell segments with piezoelectric layers and generalized curvature subjected to external pressure. The analysis incorporates several typical meridian shapes, including circular, parabolic, and half-sinusoid geometries. The paper uses Donnell shell theory (DST), combined with von Kármán geometric nonlinearity and an improved Lekhnitskii smeared stiffener technique to study the behavior of stiffened spiral or orthogonal FG-CNTRC shells. The carbon nanotube (CNT) distributions in the shells and stiffeners are designed to satisfy material continuity conditions. Thermal effects and elastic foundation interactions are also incorporated into the analysis, providing a comprehensive framework for understanding their influence on structural stability. To examine large deformation behavior, three-term deflection functions fulfilling the simply supported boundary conditions are adopted, whereas the Ritz energy approach is utilized to derive the load-deflection relationship under external pressure. The numerical results indicate that the critical buckling loads and postbuckling responses are significantly affected by the spiral stiffener system, elastic foundation, temperature variations, and CNT distributions.

Nonlinear thermo-mechanical buckling responses of FG-GPLRC catenary caps and circular plates

Kieu Quang Thai , Bui Tien Tu, Cao Cong Anh — Fri, 26 Dec 2025 00:00:00 +0000

An analytical framework is developed to investigate the nonlinear thermal and mechanical buckling behavior of functionally graded graphene platelet-reinforced composite (FG-GPLRC) catenary caps resting on nonlinear elastic foundations. The formulation is based on the first-order shear deformation theory (FSDT) coupled with von Kármán-type geometric nonlinearity. The cap geometry follows a catenary profile, from which spherical caps and circular plates emerge as special cases when the curvature radius is constant or tends to infinity, respectively. The graphene platelets are embedded within a copper matrix and graded through the thickness using various distribution patterns. By employing the Galerkin method, explicit expressions for thermal critical loads and postbuckling paths under both thermal and external pressure are derived. A comprehensive parametric study is performed to examine the influences of cap geometry, foundation parameters, and GPL distribution on the stability characteristics, offering insights into the design of curved FG-GPLRC structures under combined loading conditions.

Nonlinear buckling and postbuckling responses of sandwich cylindrical panels with layered corrugated FG-GRC core resting on elastic foundation

Nguyen Thanh Trung, Vu Minh Duc, Vu Tho Hung — Thu, 25 Dec 2025 00:00:00 +0000

An analytical framework is developed to investigate the nonlinear buckling and postbuckling behavior of sandwich cylindrical panels composed of functionally graded graphene-reinforced composite (FG-GRC) face sheets and a layered corrugated FG-GRC core. The panels are subjected to axial compression and external pressure while resting on Pasternak elastic foundations in a thermal environment. A modified homogenization model is proposed for the layered FG-GRC corrugated core, extending previous formulations of single-layer configurations to include thermal effects. Two types of corrugation geometries, trapezoidal and round, are considered, and various graphene distribution patterns are applied to optimize the stiffness of the FG-GRC core. The governing equations are derived using Donnell-type shell theory in conjunction with von Karman geometric nonlinearity, and the Ritz energy method is employed to obtain the critical buckling load expression and postbuckling equilibrium paths. Parametric studies are conducted to assess the influence of core geometry, graphene distribution, elastic foundation stiffness, thermal effects, and panel dimensions. The results highlight the substantial improvements in structural stability offered by layered corrugated cores and provide valuable insights for the design of advanced FG-GRC sandwich structures under combined mechanical and thermal loads.

Thermo-Mechanical Post-Buckling Analysis of 3D Graphene Foam Shallow Spherical Shells and Circular Plates Stiffened by a Spider-Web Stiffener System: A Stress Function Approach

Dang Thuy Dong, Nguyen Thi Thanh Hoai, Doan Lan Phuong — Thu, 25 Dec 2025 00:00:00 +0000

This study focuses on analyzing the nonlinear postbuckling response of shallow spherical shells and circular plates resting on a nonlinear elastic foundation and subjected to combined mechanical and thermal loads. The spherical shell or circular plate is made of 3D graphene foam material and is stiffened by a spider-web stiffener system, which is also composed of 3D graphene foam. The fundamental formulations and governing equations are derived based on Donnell’s shell theory, incorporating von Kármán geometric nonlinearity. The stiffness components of the stiffened plate/shell structures are determined using the extended stiffener-smearing technique. By employing the stress function approach and the Ritz energy method, analytical expressions for the load-deflection relationship are obtained. Numerical examples are then carried out to investigate the postbuckling behavior of the stiffened shallow spherical shells and circular plates under the influence of material, geometric, and foundation parameters.

Thermally induced nonlinear instability of functionally graded plates including pores and elastic edge restraint

Hoang Van Tung, Vu Thanh Long, Duong Thi Ngoc Thu — Tue, 30 Dec 2025 00:00:00 +0000

This study peruses the thermally induced nonlinear instability of rectangular plates made up functionally graded material (FGM) with porosity and elastic edge restraint. The pores are distributed in FGM via even and uneven patterns. The temperature-dependent (T-D) properties of constitutive materials are considered and effective properties of porous FGM are evaluated adopting a modification of mixture rule. Fundamental equations of nonlinear instability problem are derived employing first order shear deformation theory (FSDT) incorporating geometric imperfection and interactive pressure from two-parameter foundation. Analytical solutions of transverse displacement, stress function along with rotations are used to fulfil simply supported conditions on boundary edges and Galerkin procedure combined with an iterative process are employed to obtain critical temperatures and post-buckling paths. Parametric studies explore that porosity beneficially influences the buckling withstanding and post-buckling strength of thermally loaded FGM plates. In contrast, tangential constraints of edges have deteriorative effects on nonlinear instability of porous FGM plates undergoing thermal loadings.

RAG-IT: Retrieval-Augmented Instruction Tuning for Automated Financial Analysis - A Case Study for the Semiconductor Sector

Van-Duc Le, Tien-Cuong Bui, Hai-Thien To — Thu, 25 Dec 2025 00:00:00 +0000

Financial analysis relies heavily on the interpretation of earnings reports to assess company performance and guide decision-making. Traditional methods for generating such analyses require significant financial expertise and are often time-consuming. With the rapid advancement of Large Language Models (LLMs), domain-specific adaptations have emerged for financial tasks such as sentiment analysis and entity recognition. This paper introduces RAG-IT (Retrieval-Augmented Instruction Tuning), a novel framework designed to automate the generation of earnings report analysis through an LLM fine-tuned specifically for the financial domain. Our approach integrates retrieval augmentation with instruction-based fine-tuning to enhance factual accuracy, contextual relevance, and domain adaptability. We construct a sector-specific financial instruction dataset derived from semiconductor industry documents to guide the LLM adaptation to specialized financial reasoning. Using NVIDIA, AMD, and Broadcom as representative companies, our case study demonstrates that RAG-IT substantially improves a generalpurpose open-source LLM and achieves performance comparable to commercial systems like GPT-3.5 on financial report generation tasks. This research highlights the potential of retrieval-augmented instruction tuning to streamline and elevate financial analysis automation, advancing the broader field of intelligent financial reporting.

Semi-analytical approach for nonlinear dynamic responses of complex curved functionally graded graphene metal matrix reinforced panels subjected to impulse loads

Nguyen Thi Phuong, Kieu Lan Huong, Truong Thi Hue — Thu, 25 Dec 2025 00:00:00 +0000

This study develops a semi-analytical framework to investigate the nonlinear dynamic behavior of functionally graded graphene-reinforced metal matrix composite (FG-GRMMC) shallow panels with complex curvatures under thermal environments. Three panel geometries, cylindrical, parabolic, and sinusoid, are examined under impulsive loading conditions, including finite duration step and triangular blast loads. The analysis is formulated within the higher-order shear deformation theory (HSDT), incorporating von Kármán geometric nonlinearities. To address the geometric complexity, the stress function is approximated using an average-based like-Galerkin technique that satisfies the compatibility condition. The nonlinear governing equations of motion are derived via the Lagrange principle, with structural damping modeled through the Rayleigh dissipation function. Numerical simulations employing the fourth-order Runge-Kutta method are conducted to capture the time-dependent deflection responses. The results provide insights into the influence of panel geometry, graphene distribution, and impulse load characteristics on the nonlinear dynamic performance of FG-GRMMC panels.

Building a miniature experimental model for camouflage underwater explosions

Thang Dam Trong , Viet Duc Tran, Hieu Vu Trong, Dao Dac Hoang — Thu, 25 Dec 2025 00:00:00 +0000

In general, explosion experiments on miniature models are research methods commonly used in explosion research. Although the method of experimental explosion research on miniature models in laboratory conditions is very meaningful for practical application but up to now, there have been no published papers on the method of calculating and designing parameters on the size of miniature models that satisfy the conditions of camouflage underwater explosions (UNDEX), so that similar explosive effect laws when carrying out UNDEX in rivers and seas can be drawn, whose factors converting research results from miniature models to reality are also obtained. For the above reason, the paper aims to analyze the theoretical basis of the similarity model of an explosion, proposing a method for calculating and verifying the parameters of miniature experimental models on underwater explosion effects, conducting experiments, and establishing experimental laws. The result is a miniature model for experimental research on underwater explosions that satisfies the conditions of blasting in infinite environments and satisfies the similarity principle of shock wave pressure in water environments with a model correction factor of 1.45 to 1.47 times when compared to the methods of Russia and the United States, respectively.

Nonlinear dynamic responses of functionally graded graphene platelet reinforced composite spherical caps subjected to impulse loads

Nguyen Trong Tam, Pham Nhu Nam, Nguyen Thi Giang — Sat, 27 Dec 2025 00:00:00 +0000

This paper investigates the nonlinear dynamic behavior of functionally graded graphene platelet reinforced composite (FG-GPLRC) shallow axisymmetric spherical caps resting on a nonlinear viscoelastic Pasternak foundation and subjected to transient mechanical loading. The caps are exposed to a thermal environment, yet the mechanical properties of the material are considered temperature-independent. The theoretical framework is established based on higher-order shear deformation theory (HSDT) integrated with von Karman geometric nonlinearity. The governing equations of motion are derived using the Lagrangian approach, incorporating damping effects through the Rayleigh dissipation function. A semi-analytical solution is obtained by combining the Ritz method for spatial discretization and the Runge-Kutta method for time integration. Two forms of impulsive pressure, infinite duration step load and blast load, are examined to evaluate transient responses. Parametric studies are conducted to explore the effects of graphene distribution patterns, mass fraction, geometric parameters, thermal pre-deflection, foundation stiffness, and damping coefficients on the nonlinear response.

Nonlinear dynamical response of FG sandwich plates with pores and flexibly constrained boundaries in thermal environments

Nguyen Van Thinh, Be Ngoc Son, Hoang Van Tung — Sun, 28 Dec 2025 00:00:00 +0000

The present article scrutinizes the nonlinear transient response (NTR) of functionally graded material (FGM) sandwich plates including the simultaneous impacts of pores, geometric perturbation, high temperature, and flexible constraints of boundaries. The characteristics of constitutive materials are depended on temperature and overall features of imperfect FGM are sought employing a modification of linear rule of mix. Two sandwich configurations fabricated from FGM and homogeneous layers are considered, and pores are evenly distributed in materials. Fundamental derivations via transverse displacement along with stress function (SF) are based on the first order plate theory (FOPT) incorporating initial geometric imperfection and von Kármán terms. The derived equations are resolved by adopting analytic solutions combined with Galerkin approach to yield a differential equation with nonlinear terms. The derived differential equation is resolved by virtue of taking up the Runge–Kutta integration diagram to graph the temporal transverse displacement (TD)–time curves of transient response of sandwich plates. An illustrative analysis is implemented to evaluate diverse impacts of pore volume ratio, imperfection, tangential restraints of boundaries, and high temperature on the nonlinear transient response. It is explored that in-plane edge confinements substantially influence the nonlinear dynamic response, especially at high temperatures. Furthermore, the thickness of skins and size of geometrical imperfection significantly affect temporal TD–time paths.

Assessing the Determinants of Maintenance Effectiveness in Aged Buildings Using Structural Equation Modeling: An Empirical Study in Vietnam

Thi-Cam Tien Ngo, Thanh-Tan Le, Trung-Hieu Le, Duc-Hoc Tran — Thu, 25 Dec 2025 00:00:00 +0000

Effective management of aging buildings presents significant economic and technical challenges, particularly in large urban centers such as Ho Chi Minh City, Vietnam, where numerous high-rise structures were constructed prior to 1975. Because operation and maintenance can comprise nearly 80% of overall life-cycle costs, pinpointing the factors that impede maintenance effectiveness is of vital importance. The present study constructs and validates a model to examine and quantify the critical factors that hinder Building Maintenance Effectiveness (BME). The study was carried out using Partial Least Squares Structural Equation Modeling (PLS-SEM) with data obtained from 147 valid responses of maintenance experts in Ho Chi Minh City, Vietnam. The suggested model exhibits substantial explanatory capacity, clarifying 74.5% of the variance in BME (R² = 0.745). The analysis reveals five statistically significant negative determinants: Building Management Factors (BMF), Budget and Financial-Related Factors (BFRF), Technical-Related Factors (TRF), Technology Application-Related Factors (TARF), and Building User-Related Factors (BURF). Among these, deficiencies in technology application (TARF) emerged as the most critical barrier (f² = 0.351), followed by moderate effects from management (BMF) and financial (BFRF) constraints. The study provides a data-driven analytical framework to support facility managers and policymakers in prioritizing investment resources, while emphasizing technology adoption as the most strategic intervention for optimizing performance and ensuring sustainable development of building assets.