https://jst.vn/index.php/etsd en-US jst@hust.edu.vn (JST - Engineering and Technology For Sustainable Development) jst@hust.edu.vn (JST - Engineering and Technology For Sustainable Development) Sun, 15 Mar 2026 00:00:00 +0000 OJS 3.2.1.1 http://blogs.law.harvard.edu/tech/rss 60 https://jst.vn/index.php/etsd/article/view/1330 The study focuses on applying chemical agents to alter char obtained from the pyrolysis of rubber. The findings indicate that the collaborative using of potassium hydroxide (KOH) and HCl yields superior efficiency relative to their individual use. The carbon content in the modified char escalates from 69.9% to 85.5%, the BET-specific surface area experiences an approximate tripling (from 52 cm²/g to 143 cm²/g). Additionally, the mineral constituents, including Si, Ti, Ca, and Zn, as revealed by energy-dispersive X-ray spectroscopy (EDS) analysis, are markedly diminished, particularly Si, which declines from 6.4% to 0.8%. The EDS-Mapping analysis reveals a sparse distribution of the aforementioned metals following the modification process. The fourier transform infrared spectroscopy (FT-IR) analysis further substantiates that the vibrational intensity of the Si-O-Si bond is significantly diminished in the modified char sample, indicating its nearly complete removal. The capacity for toluene adsorption - desorption and oxidation performance of modified char also has been preliminarily evaluated and contrasted with that of activated carbon. Dinh Quang Ta, Manh Hung Khong, Thi Thu Hien Tran, Thanh Hung Nguyen, Van Chuc Nguyen, Minh Thang Le Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1330 https://jst.vn/index.php/etsd/article/view/1279 The study synthesized and investigated ZnO/Al2O3 composites as potential activators for rubber vulcanization. Al2O3 was initially prepared from boehmite, followed by ZnO deposition via wet impregnation with varying Zn(NO3)2 solution concentrations. This approach yielded a series of composite 10%, 15%, 20%, 25%, 30%, 35%, and 40% ZnO. Comprehensive characterization was conducted using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, particle size distribution, and scanning electron miscroscopy (SEM). XRD analysis confirmed the formation of g-Al2O3 and the deposition of nano-sized ZnO onto the Al2O3 surface. SEM examination demonstrated that the porous structure of Al2O3 was preserved, particularly in the in 20% ZnO/Al2O3 sample, which was therefore was selected for the natural rubber (NR) vulcanization study. The NR compound containing 10 phr of 20% ZnO/Al2O3 exhibited a steady torque increase over time, with an extended optimal cure time compared to compounds containing conventional ZnO (2 phr) and Al2O3 (8 phr) individually and their physical mixture. Despite the longer cure time, this formulation achieved superior tensile strength and elongation at break. These improvements are attributed to the synergistic effects between ZnO and Al2O3, where ZnO promotes crosslink formation while Al2O3 helps suppress the overcuring typically caused by ZnO. Thi Thuong Nghiem, Minh Tien Nguyen, Hoang Trung Nguyen, Han Long Nguyen Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1279 https://jst.vn/index.php/etsd/article/view/1280 Lead-free piezoelectric ceramic of (0.94-x)[(Bi0.5Na0.5)TiO3] + 0.06BaTiO3 + xSrTi0.875Nb0.1O3 (abbreviated as BNBT-xSTN) with x equal 0.0, 0.1, 0.2, 0.3, and 0.4 were synthesized using solid state reaction. The mixing of raw materials was ball milled in alcohol for 24 hours and then calcined at 850 oC for 2 hours to form BNBT-xSTN powder. The BNBT-xSTN powders were further shaped and sintered at 1175 °C with a heating rate of 5 °C per minute and held at the sintering temperature for 2 hours. The crystal structure, microstructure, dielectric, ferroelectric, strain, and energy storage density of the BNBT-xSTN ceramics were systematically investigated. The BNBT-xSTN ceramic materials were analyzed using X-ray diffraction (XRD), all samples show a typical perovskite structure without any trace of secondary phase with a crystal structure coexisting in rhombohedral and tetragonal phases (R&T). Scanning electron microscopy (SEM) images showed the grain boundaries and porosity. The highest dielectric constant was 2511 at x equal 0.2. On the other hand, polarization and strain of STN doped on BNBT were induced with various electric fields E equal 40 to 60 kV/cm, the electric field-induced strain curves of the analyzed samples show a phase transition from a ferroelectric phase to a relaxor phase when the STN is doped. The x equal 0.1 sample showed the maximum energy storage density of 0.3 J/cm3 at E equal 60 kV/cm, corresponding to the Wrec/Emax value of approximately 5 × 10- 3 J/(kV.cm2). Vu Diem Ngoc Tran, Thi Thao Nguyen, Thi Hinh Dinh, Van Cuong Tran Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1280 https://jst.vn/index.php/etsd/article/view/1281 The electrocaloric effect in ferroelectric materials has gained significant interest for the development of solid-state cooling devices. However, achieving a high electrocaloric effect near room temperature is still challenging. In the study, we employ a phase-field simulation approach to investigate the impact of zirconium (Zr) doping on the electrocaloric behavior of barium titanate zirconate, BaZrxTi1-xO3 (0% ≤ x ≤ 20%) ferroelectric thin films. Our results reveal that Zr doping significantly modifies the domain structures and phase transition dynamics, thereby enhancing the electrocaloric performance, particularly near room temperature. Isothermal entropy and adiabatic temperature variations are enhanced with increasing Zr doping content in BaZrxTi1-xO3 thin films. The highest electrocaloric effect is observed in the BaZr0.2Ti0.8O3 thin film, at near room temperature, corresponding to the transition from ferroelectric to paraelectric phase. Moreover, the BaZr0.2Ti0.8O3 thin film also indicates a large entropy change at a low electric field and thus a large electrocaloric strength, which is beneficial for practical cooling at low voltages. These findings highlight the potential of Zr-doped BaTiO3 thin films as promising candidates for energy-efficient solid-state cooling applications operating near room temperature. Thi Ha Dang , Ba-Hieu Vu, Thi Hong Hue Dang, Trong-Giang Nguyen, Van-Hai Dinh, Van Lich Le Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1281 https://jst.vn/index.php/etsd/article/view/1282 The study investigates the complex interactions of ions near the electrode surface, where phenomena such as ion overcrowding and overscreening significantly influence ion transport and electrokinetic behavior. Under the application of a large voltage, intense electrostatic forces act on ions near the electrode, causing substantial modifications to the electric double layer (EDL) structure and the spatial charge distribution. These effects are particularly pronounced in systems with high ionic concentrations, where steric hindrance and ion size disparities become critical. The classical Poisson-Nernst-Planck (PNP) model is inadequate for describing these phenomena, as it neglects steric effects and fails to account for ion-ion interactions in dense ionic environments. To overcome these limitations, the modified Poisson-Nernst-Planck (mPNP) model is employed. This model incorporates key factors such as ion size effects and ion-ion interactions, enabling the accurate simulation of phenomena including the formation of densely packed EDLs and ion dispersion under extreme conditions. Additionally, the mPNP equations are coupled with the Navier-Stokes equations to provide a comprehensive representation of ion transport and fluid dynamics. This integrated framework facilitates a deeper understanding of the interplay among electrostatic forces, fluid flow, and steric hindrance, offering critical insights into the behavior of electrochemical systems under high-voltage and high-concentration conditions. Van Quyet Ngo, Van Sang Pham Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1282 https://jst.vn/index.php/etsd/article/view/1187 Vanadium pentoxide (V₂O₅) was rapidly synthesized from vanadium metal powder using a microwave-assisted method, completing the entire process in less than one hour. The resulting material exhibited a wrinkled nanosheet morphology. The synthesized V₂O₅ showed enhanced photoresponsivity, with the photocurrent increasing by approximately 1.8 times under 470 nm illumination. In addition, the material exhibited excellent ambient stability, with negligible signal degradation after 30 days. Structural and optical properties were systematically characterized by X-ray diffraction (XRD), Raman spectroscopy, and UV–Vis spectroscopy, revealing clear correlations between synthesis conditions, crystal structure, and optical behavior. These findings highlight microwave-assisted synthesis as a fast and efficient strategy for fabricating V₂O₅-based materials for photodetectors and other optoelectronic applications. Tuan Sai Vu, Thanh Nghi Nguyen, Huu Phuoc Luong, Duc Vuong Dang, Xuan Hien Vu Copyright (c) 2025 https://jst.vn/index.php/etsd/article/view/1187 https://jst.vn/index.php/etsd/article/view/1283 The study focuses on clarifying the fluctuations of indoor fine particle concentrations under different conditions and identifying the main factors contributing to this exposure. The light scattering method (by using ATMOtube real-time monitor) was evaluate by comparing it with the gravimetric reference method (by using MiniVol TAS 5.0 for sampling and weighing under our Lab conditions). The two methods were first tested according to standard procedures to ensure its stability and accuracy, next implemented simultaneously for comparison, and then the light scattering method was applied to 14 apartments in Hanoi for 24 hours, recording PM2.5 and PM10 concentrations. The research results show that: 1) PM2.5 and PM10 concentrations are similar, proving that the indoor particulate matter is mainly PM2.5; 2) the levels of fine particle PM2.5 pollution in high-rise apartments in Hanoi is at alarming levels, which are much higher than the WHO recommended levels. The main influencing factors such as residential area location associated with outdoor environmental conditions (density of traffic and construction activities), living habits (opening windows, smoking, using gas stoves), and the presence of fine particle reduction equipment were carefully analysed. The study results also demonstrate the effectiveness of using air purifiers in controlling indoor fine particle, helping to maintain a more stable environment during the day and night. Tran Tuan Kiet Dang , Giang Thu Ton, Thi Anh Tuyet Nguyen Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1283 https://jst.vn/index.php/etsd/article/view/1284 The study used the co-precipitation method to synthesize silver (Ag) doped ZnO nanoparticles with different doping contents of 0.5%, 1%, 2%, and 3% (mole fraction). The obtained material properties were tested using methods such as energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The photocatalytic activity of these materials was assessed by degrading methylene blue (MB) using UV-Vis absorption spectra under ultraviolet, xenon, and sunlight. The antibacterial activity was evaluated using the Kirby-Bauer disc diffusion method against the gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacteria. The results demonstrate that Ag-doped ZnO nanoparticles exhibit a significant increase in photocatalytic performance and antibacterial activity over the undoped ZnO nanoparticles. The sol-gel coating technique was used to attach Ag-doped ZnO nanomaterials to enhance some unique properties of cotton fabrics, such as antibacterial and photocatalytic properties. The ASTM D4265 (Evaluating Stain Removal Performance in Home Laundering) standard was used to evaluate the effectiveness of the coating after washing cycles. Analyzing the adhesion ability of the coating based on SEM, EDS, and FTIR, the ASTM E2149 standard is used to evaluate the antibacterial efficacy of the material. Phuong Linh Nguyen, Duy Nam Phan, Minh Thang Le Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1284 https://jst.vn/index.php/etsd/article/view/1285 The study was conducted to develop a smart production preparation model for industrial garment enterprises. In this research, a questionnaire survey and interviews were used to collect data from 100 garment enterprises in Vietnam. The survey aimed to assess the current status of applying Industry 4.0 achievements and technologies such as radio frequency identification (RFID), artificial intelligence (AI), and 3D technology in various production preparation stages (including material and accessory preparation, sample development, and preparation of technical and technological documentation). Based on the findings, a smart production preparation model is proposed, incorporating the full application of these technologies and analyzing the interrelationships among the model’s components. The results also reveal several challenges and the feasibility of applying these technologies in different parts of the smart production preparation model for Vietnamese garment enterprises. The study also provides several recommendations to support the effective implementation of this model, directed at both the government and enterprises. Thi Huong Nguyen, Thi Lua Pham Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1285 https://jst.vn/index.php/etsd/article/view/1286 The natural gas supply in Vietnam is progressively declining; therefore, the strategy of importing LNG (Liquefied Natural Gas) is currently an urgent solution to ensure national energy security. The main component of LNG is methane, which is liquefied through deep refrigeration for storage and transportation. According to Power Development Plan VIII, by 2030, the country is expected to have about 24 GW of power generated from LNG. Ensuring stable flow (flow assurance) is a key factor in the LNG transportation system. This study focuses on calculating the operating conditions in the LNG supply pipeline using OLGA software. Based on the transported gas flow rate, the study conducts steady-state simulations as the basis for calculating the transient state of the pipeline. The transient results indicate the need to reinforce the initial segment of the pipeline with thermally insulated alloy steel, control hydrate formation using hydrate inhibitors, conduct regular pigging, assess the risk of system shutdown, and manage depressurization operations. These results serve as a foundation for the effective and safe design and operation of the LNG supply system. Hai Nam Chu, Duc Huy Quach, Duc Duong Pham Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1286 https://jst.vn/index.php/etsd/article/view/1287 This study introduces a novel predator-prey model that integrates the effects of predator intraspecific competition, prey group defense mechanisms, wind flow, and harvesting effort. The model employs a modified Holling type II functional response to capture the complexity of prey-predator interactions under environmental and anthropogenic influences. We establish the model’s positivity and boundedness and derive conditions for the local and global stability of equilibrium points. Hopf bifurcation analysis reveals that both wind intensity and harvesting effort significantly affect system stability. Numerical simulations demonstrate that while mild wind flow can stabilize the system with minimal group defense, increased wind intensity enhances overall system stability. Furthermore, harvesting pressure and intraspecific competition contribute to stability regardless of wind strength. The analysis also shows that intraspecific competition and harvesting effort are positively correlated with prey density and negatively correlated with predator density at equilibrium. Phuong Thuy Nguyen, Duc An Van, Thi Thoa Trieu Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1287 https://jst.vn/index.php/etsd/article/view/1293 The paper presents a systematic quantitative literature review of Vietnamese Sign Language recognition techniques developed between 2015 and 2025. VSL recognition plays a vital role in bridging communication gaps and enhancing accessibility for the deaf and hard-of-hearing community in Vietnam. To identify and synthesize current trends and challenges, we conducted a structured search and screening process across major academic databases. These works were analyzed based on recognition approach (e.g., computer vision, wearable sensors, data-driven methods, and multimodal data fusion), datasets used, feature extraction strategies, classification models, and performance metrics. Descriptive statistics were used to map the evolution of methods over time, while comparative analyses highlighted the strengths and limitations of different techniques across real-time and static recognition tasks. Our findings indicate a growing shift towards deep learning and sensor fusion methods, though limitations persist in dataset availability, model generalizability, and real-world deployment. This review provides critical insights into current research gaps and offers guidance for future work on scalable, culturally adaptive VSL recognition systems. Quang Huy Hoang, Ngoc Tram Nguyen, Huu Trung Nguyen, Ngoc Anh Nguyen, Thi Viet Huong Pham, Anh Vu Tran Copyright (c) 2026 https://jst.vn/index.php/etsd/article/view/1293