Suranaree Journal of Science and Technology

DERIVATION OF MATHEMATICAL MODEL FOR THE DC HEAVY RAIL SYSTEM USING THE DQ METHOD

2025-10-25T19:12:30+07:00

The electric railway system is an efficient mode of transportation capable of carrying a large number of passengers per trip, thereby reducing travel time and operational costs. As a result, its use has been increasing, following the technological advances. To accurately analyze the behavior of this system, an accurate mathematical model is required. Herein, the DQ method is employed to obtain a time-invariant model via the transformation of time-varying AC signals into DC quantities within a synchronous rotating reference frame. The derived model can be applied to various railway system development applications, including stability analysis, instability mitigation, and the study of dynamic behavior. To verify the accuracy of the proposed model, simulation is employed to validate its dynamic responses by comparing them with those obtained from the SimPowerSystem block set in MATLAB. The results confirmed that the derived mathematical model can accurately capture both the transient and steady-state responses. Furthermore, compared to the exact topological model implemented in MATLAB, the proposed model significantly reduces the computational time by 97%.

FRACTURE BEHAVIOR CHARACTERIZATION OF NORMAL AND HIGH-STRENGTH CONCRETE USING SIZE EFFECT LAW AND FINITE ELEMENT MODELLING

2025-10-22T09:03:37+07:00

This study investigates the fracture behavior of normal and high-strength concrete through experimental analysis, theoretical models, and finite element simulations. A series of notched concrete beam specimens with varying notch-depth ratios were subjected to three-point bending tests to evaluate fracture parameters, including fracture energy (Gf), fracture toughness (K_IC), fracture process zone length (FPZ), and characteristic length (l_ch). The size effect method developed by Bažant was employed to assess the dependency of the fracture parameters on the specimen geometry and notch ratio. The results reveal a significant influence of the notch-depth ratio on brittleness, energy dissipation, and crack propagation. Additionally, finite element modelling (FEM) using ANSYS was used to validate the stress intensity factors and deformation characteristics observed experimentally. A comparative analysis between normal and high-strength concrete confirmed that high-strength concrete exhibits a more brittle response with higher fracture energy but reduced fracture process zone length. This comprehensive evaluation highlights the applicability of nonlinear fracture mechanics for quasi-brittle materials such as concrete and supports the incorporation of fracture-based parameters into advanced design codes.

FROM SPARKS TO PRECISION: PARAMETRIC OPTIMIZATION OF WIRE EDM FOR EFFICIENCY AND ACCURACY IN AL 6113 ALLOY MACHINING

2025-11-10T16:23:28+07:00

Wire-Electro Discharge Machining (WEDM) is a promising non-traditional machining process for aluminium alloys, which are otherwise difficult to machine using conventional methods due to plastic deformation and the formation of heat-affected zones. In the present study, the machinability of Al 6113 alloy was investigated under varying WEDM parameters using a Taguchi L9 orthogonal design. The influence of pulse-on time, pulse-off time, and peak current on material removal rate (MRR), kerf width, and surface morphology was systematically evaluated. The results indicate that pulse-on time is the most significant factor influencing both MRR and kerf width, while pulse-off time also plays a critical role in determining machining efficiency. Surface morphology analysis revealed that higher discharge energy conditions led to the formation of microcraters, micropores, and recast layers, whereas optimized parameters improved surface integrity. In addition, a Pareto front-based multi-objective optimization was employed to balance MRR and kerf width, identifying non-dominated solutions and a knee point for improved trade-offs between productivity and machining accuracy. The findings highlight the effectiveness of WEDM in machining Al 6113 alloy and establish its potential for precision applications in aerospace and automotive industries.

MICROWAVE-SYNTHESIZED Sr₂ZnMoO₆:Eu³⁺ PHOSPHORS IN TeO₂–ZnO–BaO GLASS: STRUCTURAL, OPTICAL, AND LUMINESCENCE PROPERTIES FOR POTENTIAL REDDISH-ORANGE SSL APPLICATIONS

2025-01-24T15:21:45+07:00

The Sr₂ZnMoO₆ phosphor was incorporated into TeO₂: ZnO: BaO glass using the microwave synthesis, with different amount of phoshors (0.00, 2.50, 5.00, 7.50, and 10.00 wt%). The samples were characterized through density, refractive index, XRD, FTIR, absorption spectra, luminescence properties, and lifetime analysis. The crystalline structure was analyzed by using X-ray diffractometer and compared with the standard Sr₂ZnMoO₆ crystal structure. Absorption spectra analysis showed four peaks associated with the transitions of Eu³⁺ ion, while photoluminescence was observed between 550 and 725 nm when excited at 465 nm. The emission intensity increased as the concentrations of Sr₂ZnMoO₆ phosphor increased up to 7.50 wt%, after which it decreased. These samples exhibited a high photoluminescence quantum yield of 56.49%, with the high-intensity peak observed at 614 nm, corresponding to the ⁵D₂ → ⁷F₀ (reddish orange) transitions of Eu³⁺ ion. The luminescence lifetime values from the ⁵D₂ → ⁷F₀ state decreased (0.891, 0.886, 0.880, and 0.874 ms) by adding a concentration of phosphors, The results indicate that these samples have the potential to be used in solid-state lighting applications.

PERFORMANCE ENHANCEMENT OF CONCRETE USING SAP-MK HYBRID SYSTEM: STRENGTH, DURABILITY, AND SELF-HEALING MECHANISMS

2025-10-21T08:56:12+07:00

This study presents a performance-driven approach to enhancing the mechanical, durability, and self-healing characteristics of M40-grade concrete through the combined use of metakaolin (MK) and superabsorbent polymers (SAP). The experimental program involved twenty concrete mixes comprising control, MK- and SAP-modified, and hybrid systems evaluated for strength, transport properties, and autogenous crack-healing over 7, 28, and 56 days, with supporting microstructural analysis via SEM-EDS. Results demonstrate that MK enhances strength and matrix densification through pozzolanic reactivity, while SAP promotes sustained hydration and autonomous crack closure. The hybrid SAP-MK systems exhibited the most significant improvements across all performance metrics, with microstructural evidence confirming pore refinement and formation of secondary hydration products. The novelty of this work lies in the synergistic integration of MK and SAP into a unified mix design that addresses multiple performance limitations of conventional concrete simultaneously. This research offers a sustainable, field-applicable solution for developing durable, self-healing concrete suited to aggressive service environments, with clear implications for extending infrastructure lifespan and reducing long-term maintenance demands.

DESIGN OF INTELLIGENT BLDC MOTOR ARCHITECTURES FOR THE NEXTGEN ELECTRIC VEHICLES

2025-09-11T09:46:40+07:00

One of the cornerstones of developing energy-efficient policies in the field of electric mobility is the arrival of brushless direct current (BLDC) motors. In this paper, a detailed discussion of the BLDC motor systems is presented, including the design, modelling, and control strategies to ensure more efficient use of the motor system to achieve greater energy efficiency in car motors. The paper talks about the principles of the work of the BLDC motors as well as the use of position sensors, electronic commutation, and the dynamics of the inverter. The mathematical model of BLDC motors is described in detail, with the focus being placed on the reduction of the highly complicated 3-phase systems to simpler d-q reference frames to simplify the analysis. A range of control methods, including proportional-integral-derivative (PID) controllers, is also examined in the research, and the importance of their role in obtaining accurate control of speed and torque is mentioned. Introduction of power electronics, such as inverters and pulse-width modulation (PWM) methods, is also dealt with to enhance the efficient functioning of a motor. Moreover, the paper discusses closed-loop control systems that stabilise and operate under a diverse environment, and this is fundamental to the application of electric vehicles. Transient analysis and dynamic response of the BLDC motors are given special attention so as to optimise the use of energy. The work will be used as a reference guiding researchers and engineers who want to develop the current technology of the BLDC motors to achieve sustainable electric mobility systems.

CARBON-OPTIMIZED BUILDING MASSING WITH CONSTRUCTIVE SOLID GEOMETRY STRATEGIES: A PARAMETRIC MULTI-OBJECTIVE FRAMEWORK

2025-10-27T14:10:37+07:00

The early-stage performance of architectural design is critical for long-term carbon optimization. This study investigates three constructive solid geometry (CSG) strategies, namely union, subtraction, and intersection, within a parametric workflow driven by the Non-dominated Sorting Genetic Algorithm II (NSGA-II), aiming to minimize operational carbon emissions (OCE) and maximize gross floor area (GFA). It connects geometric design logic with objectives to support carbon-conscious massing decisions. The study examines how CSG strategies influence simulation runtime, model validity, and design diversity; how NSGA-II optimizes form generation under regulatory constraints e.g., floor area ratio (FAR), open space ratio (OSR); and how these affect early-stage outcomes. Out of 3,000 generated configurations, the subtraction strategy achieved the lowest operational carbon intensity (181.30 kgCO₂eq/m² at 45,901.85 m² GFA) and provided greater design diversity with 151 valid configurations, while the intersection strategy demonstrated the fastest simulation runtime of 3h 40m 40s. The proposed framework effectively filtered infeasible designs and ensured regulatory compliance to maintain model validity. Convergence of optimal OCE values (~181 kgCO₂eq/m²) across strategies suggests a useful benchmark for high-rise office buildings in dense urban contexts. These findings highlight the value of integrating carbon optimization, regulatory constraints, and multi-objective parametric design into early-stage architectural workflows to improve sustainability.