Vietnam Journal of Science, Technology and Engineering

Parameter optimisation for single-track laser cladding using the Taguchi-Grey relational approach

2026-06-17T05:24:33+07:00

The judicious selection of laser cladding (LC) process parameters is essential for the clad bead geometry. In this research, the Taguchi-Grey relational method was chosen to enhance the quality of single-track bead geometry and to perform multi-objective optimisation of process parameters. The Taguchi method was selected to construct an L16 orthogonal experiment. The impact of significant LC parameters (laser power (P), scanning speed (S), and powder feeding rate (F)) on the responses (width (W), height (H), penetration (Pene), and dilution rate) was analysed based on the analysis of variance (ANOVA). The findings indicated that the scanning speed was the most important factor affecting the ratio of layer W, H, Pene, and dilution rate of the cladding. Subsequently, grey relational analysis (GRA) was employed to consolidate the four response variables into a singular grey relational grade (GRG) for quantification and optimisation purposes. Finally, the optimum cladding process parameters were obtained. The face-centred cubic (FCC) single-phase coating was observed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to analyse the microstructure and chemical composition of the coating. Moreover, hardness measurements exhibited a gradual increase from the substrate (197 HV) to the cladding layer (224 HV), attributed to the distribution of Cr and Mo, solid solution strengthening, and microstructural refinement, demonstrating improved mechanical performance.

Effect of chemical modification on the superhydrophobic properties of CT3 steel surfaces

2025-08-14T05:04:53+07:00

This study systematically explores the influence of diverse chemical surface modifications on the water-repellent properties of CT3 steel substrates, focusing on the synergistic relationship between surface topography and chemical composition in realising superhydrophobic behaviour. Initially, steel samples were coated with a ZnO layer to significantly enhance surface roughness, serving as a foundation for subsequent chemical treatments. The surfaces were then functionalised with various low-surface-energy agents, including triethoxymethylsilane (MTES), polydimethylsiloxane (PDMS), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOS), stearic acid (SA), and high-density polyethylene (HDPE). Quantitative assessment via contact angle measurements demonstrated that coatings of MTES, PFOS, PDMS, and SA successfully achieved superhydrophobicity, characterised by water contact angles greater than 150° and minimal contact angle hysteresis. Of particular interest, MTES treatment in toluene solvent not only effectively reduced the surface free energy but also promoted the formation of nanofilamentous microstructures, thereby amplifying surface roughness and hydrophobic performance. The chemically and morphologically modified surfaces were thoroughly characterised using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and detailed wettability analyses to correlate surface structure with hydrophobicity.

UV/visible-light photocatalytic degradation of organic dyes using ZnO nanomaterials

2026-06-17T05:59:52+07:00

In this study, ZnO nanomaterials were synthesised via a hydrothermal method and characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM)/high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), analysis and diffuse reflectance spectroscopy (DRS). The obtained ZnO exhibited a wurtzite structure, high crystallinity, mesoporosity, a large specific surface area of 107.17 m²/g, and a band gap of 3.19 eV. Photocatalytic performance was comparatively evaluated under visible and UV irradiation using methylene blue (MB) and Rhodamine B (RhB) as model dyes. ZnO achieved >90-98% degradation, with consistently faster kinetics under UV irradiation and MB degrading faster than RhB. Pseudo-first-order fits yielded k(MB)=0.027 min^-¹ (Vis) vs 0.076 min^-¹ (UV) and k(RhB)=0.024 min^-¹ (Vis) vs 0.066 min^-¹ (UV), linking structureproperty features to light-dependent activity. These results establish a clear UV/Vis comparison and underscore the applicability of hydrothermal ZnO for wastewater treatment under practical illumination.

Novel naphthalene-tetrazole butanamide derivatives: synthesis and evaluation of acetylcholinesterase inhibitory activity

2026-06-17T08:59:09+07:00

Acetylcholinesterase (AChE) inhibitors constitute a well-established class of therapeutic agents that provide symptomatic relief in Alzheimer’s disease, underscoring the continued importance of developing new compounds with improved efficacy and safety profiles. In this context, five novel derivatives bearing the 4-(5-(naphthalene-2-yl)-2H-tetrazol-2-yl)-N-phenylbutanamide scaffold were synthesised through four known reactions: [3+2] cycloaddition, N-alkylation, saponification, and amidation. The purity of the compounds was confirmed by melting point analysis and thin-layer chromatography (TLC). Structural characterisation was achieved using infrared spectroscopy (IR), high-resolution mass spectrometry (HRMS), and proton and carbon nuclear magnetic resonance spectroscopy (¹H-NMR and ¹³C-NMR). The acetylcholinesterase inhibitory activity of the synthesised compounds was evaluated at five concentrations to determine their IC₅₀ values. Compound IVa exhibited the highest inhibitory potency, with an IC₅₀ of 467.82±10.77 μM. In addition, the inhibitory potential of the compounds was analysed in relation to their physicochemical properties, including drug-likeness and blood-brain barrier permeability, with none violating Lipinski’s rule. Molecular docking studies further revealed that the naphthalene-containing framework demonstrated strong predicted binding affinity to AChE, which may contribute to the observed inhibitory activity. These findings provide novel and valuable structural insights for the development of AChE inhibitor derivatives as potential therapeutic strategies for Alzheimer’s disease.

Preparation and preliminary evaluation of a soothing gel containing Aloe vera and Perilla frutescens essential oil

2026-06-17T09:13:03+07:00

This article presents the process of developing an innovative skincare product derived from natural ingredients, specifically Aloe vera and perilla leaf essential oil (Perilla frutescens). The product is formulated in a gel-based form, making it lightweight, non-greasy, and suitable for a wide range of skin types, including normal, oily, combination, and especially sensitive skin. By combining clean, affordable, and easily accessible ingredients, the research has successfully created a high-quality skincare solution with excellent moisturising, protective, and regenerative properties at a relatively low production cost. The gel is rapidly absorbed into the skin, providing immediate hydration while delivering essential nutrients that help maintain healthy and balanced skin. Aloe vera extract is well known for its soothing, anti-inflammatory, and healing effects, whereas perilla leaf essential oil contributes antioxidant and skin-brightening benefits. Together, these ingredients help reduce irritation, improve skin texture, and support natural skin recovery. In addition, the product incorporates nanoparticles such as gold (Au) and titanium (Ti), which enhance skin regeneration, reduce dark spots, stimulate collagen production, and promote brighter, smoother, and healthier-looking skin with long-term use.

Application of a transport organisation model based on Transit-Oriented Development: A case study of urban railway line No. 1 in Ho Chi Minh city, Vietnam

2026-06-17T09:30:00+07:00

Metro line No. 1 is the first urban railway line in Ho Chi Minh city, traversing densely populated urban areas and major passenger attraction centres. While it offers the potential for modern transport connectivity, operational experience has revealed that the existing transport infrastructure in adjacent areas does not fully meet passenger travel demand and has not kept pace with the city’s rapid urban development. This study focuses on assessing the scientific basis and current state of transport organisation, with the aim of applying the Transit-Oriented Development (TOD) model to Metro line No. 1. The research develops and compares two simulation scenarios: (i) the current situation scenario, reflecting existing conditions of transport connectivity, and (ii) the TOD scenario, applying TOD-based transport organisation solutions. Transport network performance indicators analysed from the simulation results include travel time, level of service, accessibility, and traffic volume. Based on the analysis of current conditions, the study proposes solutions and evaluates their effectiveness through simulation results to formulate a set of TOD-based transport organisation measures. These proposals are expected to enhance the operational efficiency of Metro line No. 1 while promoting the sustainable development of Ho Chi Minh city’s urban areas.

Green energy generation from industrial wood waste: Pellet production from carbonised Eucalyptus saligna sawdust

2026-02-24T04:16:02+07:00

This study investigated the potential of pellet production from carbonised E. saligna sawdust, processed at varying particle sizes (0.6 mm, 1.18 mm, and 2.36 mm) and utilising different organic binders. Proximate and ultimate analyses of charcoal pellets were investigated using standard test methods. E. saligna sawdust was carbonised using a cylindrical barrel metal kiln, and pelletised with a manual press machine using molasses, cow dung, and fruit waste as binding agents. The proximate and ultimate analyses of charcoal pellets were determined using American Society for Testing and Materials (ASTM). Binding agents significantly influenced moisture content, volatile matter, fixed carbon, ash content, calorific value, and sulphur content (p<0.001), while particle size had a moderate effect on select parameters, particularly fixed carbon and ash content. The highest fixed carbon (44.02%) and calorific value (4980 cal/g) were observed in cow dung-bound pellets, while fruit waste-bound pellets exhibited the lowest ash (3.82%) and sulphur content (0.12%), highlighting their environmental advantages. The interaction between binding agents and particle size was significant for moisture content and volatile matter but not for fixed carbon or calorific value. This research demonstrates an innovative approach to valorise plant waste materials and underscores the potential of local biomass for sustainable energy solutions.

A new meshfree method of lines for the 3D advection-diffusion equation for solute transport in porous media

2026-06-17T05:03:43+07:00

The study proposes a novel Meshfree Method of Lines (MFMOL) for the numerical solution of three-dimensional advection-diffusion equations (ADEs) used to model solute transport in porous media. The method involves discretising the spatial variables of the model equations using an Augmented Radial Basis Point Interpolation Method (ARPIM), while the temporal variable remains continuous. This results in a system of ordinary differential equations (ODEs), which is numerically integrated using the MATLAB ODE solver. In solving solute transport in porous media, traditional mesh-based methods such as the Finite Element Method (FEM), Finite Difference Method (FDM), and Finite Volume Method (FVM) often encounter challenges such as numerical instabilities and distorted meshes caused by complex geometries and the presence of convective terms. To ensure accuracy, various stabilisation techniques are required, which increase computational effort, cost, and setup time. To overcome these challenges, the new MFMOL approach was proposed and applied in strong-form formulations without stabilisation techniques to solve 3D advection-diffusion problems in homogeneous and isotropic porous media. The results obtained were in good agreement with existing exact solutions, establishing the accuracy and efficiency of the new method and demonstrating its advantages over traditional mesh-based methods for solving problems involving complex geometries.

Vision-enabled detection of safety helmet compliance in construction zones

2026-05-11T12:09:19+07:00

In the rapidly evolving field of construction management, worker safety remains a top priority. This paper introduces an innovative vision-based system for real-time detection of helmet compliance, specifically designed for construction sites, utilising advanced computer vision techniques and machine learning algorithms within the YOLO (you only look once) framework. Our system leverages high-resolution video feeds from strategically positioned cameras to monitor adherence to safety regulations concerning helmet usage. By employing deep learning methodologies, the system effectively identifies individuals not wearing helmets, thereby significantly mitigating the risk of head injuries among workers. Our training and validation results reveal an impressive precision exceeding 97% at mAP@0.5 for both helmeted and non-helmeted individuals. Furthermore, our experiments demonstrate exceptional detection accuracy, showcasing the system’s resilience under varying lighting conditions and diverse worker movements. The consistent decrease in loss and improvement in metrics throughout training validate the effectiveness of the YOLOv8 model in enhancing recognition performance. The implications of this research extend beyond mere regulatory compliance, opening avenues for innovative applications in occupational safety management. This study highlights the critical role of technology in protecting lives and lays the groundwork for future advancements in smart construction environments.

Prediction of maintenance workforce efficiency using neural networks, fuzzy inference system and autoregressive fractionally integrated moving average for a process industry

2026-03-24T10:55:36+07:00

This study establishes the efficiency of the maintenance workforce in a process plant, utilising combined models, including artificial neural networks (ANN)-weighted aggregated sum product assessment (WASPAS) and ANNfuzzy inference system (FIS)-WASPAS. ANN models with 12 architectures and a maximum epochs ranging from 64 to 173 were the limits of the analysis. Real-life data were used to train, test and rank the different architectures. WASPAS was superimposed on the ANN model for selection and ranking purposes, while FIS rules were introduced to the ANN results to uncover the uncertainty and imprecision in the model. These results were compared with those of the autoregressive fractionally integrated moving average (ARFIMA) method. At different λ values, the 4-8-10-1 ANN architecture and the FIS with 18 rules were the fittest for the ANN-WASPAS and the ANN-FIS-WASPAS methods, respectively. The ARFIMA method revealed a coefficient of maintenance workforce efficiency of -1.8636x10-2. The constant parameter in the ARFIMA model and the root mean square error (RMSE) for the training and testing datasets are 0.9267, 0.0162, and 0.0150, respectively. In conclusion, the 4-8-10-1 ANN architecture more suitably predicts maintenance workforce efficiency than the 18-rule and ARFIMA models. This study predicts maintenance workforce efficiency, providing significant insights into the application of ANN, FIS, WASPAS, and ARFIMA models in a process industry.

Insect pests and diseases of Lai Chau ginseng (Panax vietnamensis var. fuscidiscus K. Komatsu, S. Zhu & S.Q. Cai)

2026-06-17T09:53:52+07:00

Panax vietnamensis var. fuscidiscus, commonly known as Lai Chau ginseng, is a high-value medicinal plant native to the mountainous regions of northern Vietnam. To develop effective management strategies for Lai Chau ginseng, this research aimed to comprehensively assess the pests and diseases affecting its cultivation. In 2024, a survey was conducted in Sin Ho, Lai Chau province. A total of 48 symptomatic plant samples were collected and evaluated based on morphological characteristics and visible symptoms. Four major symptom groups were identified: insect-induced leaf damage (32%), damping off (29%), leaf spots (20%), and root rot and wilting. Two key insect pests were identified: Chinavia hilaris (green stink bug) and Pseudococcus citri (mealybug), which caused significant damage to flowers, fruits, and petioles. Additionally, five pathogens were identified, including Cladosporium paeoniae (leaf spot), Puccinia sp. (rust), and three soil-borne fungi (Fusarium solani, Pythium ultimum, and Rhizoctonia solani), responsible for root rot and damping-off. These findings provide important baseline data for developing Integrated Pest Management (IPM) strategies to support the sustainable cultivation of Lai Chau ginseng.

Kaposi sarcoma in the gastrointestinal tract: Challenges in diagnosis and treatment - A case report

2025-11-06T02:26:12+07:00

Kaposi sarcoma is a vascular neoplasm involving the endothelial cells of blood and lymphatic vessels, associated with various aetiologies. While cutaneous manifestations are common, gastrointestinal involvement particularly in the stomach and colon is rare among HIV-infected individuals, accounting for only 0.2-1.2% of gastrointestinal malignancies. Epidemiologically, Kaposi sarcoma is more prevalent in males, typically between 50 and 70 years of age. We report a suspected case of gastrointestinal Kaposi sarcoma in a 22-year-old HIV-positive male presenting with chronic diarrhoea and significant weight loss. Upper and lower gastrointestinal endoscopy revealed dark red macular lesions in the stomach and infiltrative, ulcerative lesions with a reddish appearance in the sigmoid colon. This represents a rare case of gastrointestinal Kaposi sarcoma in a young individual, both in Vietnam and globally. Based on this case, we present a brief literature review of Kaposi sarcoma, with particular emphasis on gastrointestinal involvement in HIV-infected patients.

Genetic diversity and population structure of Dalbergia cochinchinensis Pierre ex Laness. in Vietnam's Central Highlands using inter-simple sequence repeat markers

2026-05-07T11:57:12+07:00

Dalbergia cochinchinensis is classified as a critically endangered (CR) species according to the 2022 IUCN Red List [1]. This study aims to assess the genetic diversity of D. cochinchinensis populations in Kon Tum, Gia Lai, and Dak Lak, located in the Central Highlands of Vietnam, using the ISSR method. In addition, it seeks to support the conservation and propagation of D. cochinchinensis. The amplified products varied in size from 150 to 3,500 bp. Out of 101 loci examined, 93 (92.08%) were found to be polymorphic, while 8 (7.92%) were monomorphic. Most primers exhibited polymorphic loci ranging from 6 to 16. ISSR analysis revealed genetic identity levels among the three populations ranging from 0.749 (Dak Lak and Kon Tum) to 0.896 (Gia Lai and Kon Tum). The total genetic diversity of the species (H_T) was calculated to be 0.261, with the average heterozygosity of the populations (H_S) being 0.166. Additionally, genetic variation within the three populations of D. cochinchinensis accounted for the majority of the total genetic variation (G_ST=0.361 and F_ST=0.432), indicating significant diversity. These findings provide important insights into the genetic structure of D. cochinchinensis, which can guide conservation and propagation efforts both in Indochina and globally.

Complete mitochondrial DNA sequences reveal the maternal genetic structure of Vietnamese Austroasiatic-speaking Bana, Hre, and Mnong populations

2026-06-17T10:06:24+07:00

Austroasiatic, a major ethnolinguistic family in Vietnam, accounts for 90% of the census population size. Apart from the majority Kinh group, 24 other Austroasiatic minorities account for 4.67% of the population, many of which remain understudied. Here, the genetic characteristics of three Vietnamese Austroasiatic ethnic groups (Bana, Hre, and Mnong) were investigated by analysing the complete mitochondrial DNA (mtDNA) of 119 individuals. A total of 6,361 polymorphic sites were identified, with Bana exhibiting the highest molecular diversity (53.64±3.51 variants per individual). Compared to hypervariable segments (HVS), complete mtDNA sequences enhanced phylogenetic resolution and accuracy. The maternal haplogroup profile consisted of 40 lineages, with 32 of the detected lineages being population specific, six shared between two populations, and two shared among all populations. The macro-haplogroup components included B, C, F, M, N, R, and Z, with 66-80% of each population assigned to haplogroups B and M. The most prevalent haplogroups were M20 (14.29%), B5a1a (6.72%), and M74b1 (6.72%). While lineages of haplogroup F were relatively more frequent in Bana and Hre, lineages of N were exclusive to Mnong, highlighting haplogroup distinctions within the Vietnamese Austroasiatic family of the Central Highlands. These findings contribute to reconstructing the complex history of migration and settlement in Vietnam.

Proposing fuel consumption limits for new vehicles to support Vietnam’s Nationally Determined Contribution

2026-06-17T10:16:50+07:00

Vietnam’s Nationally Determined Contribution (NDC) sets a target of reducing total greenhouse gas emissions in the transportation sector by 34.33%, equivalent to approximately 15.66 million tonnes of CO₂, by 2030. This study was conducted to forecast the potential for achieving that target through the application of a fuel consumption limit for cars with fewer than nine seats and for motorbikes in Vietnam. The results show that the number of new cars increased rapidly from 159,289 vehicles in 2016 to 347,287 vehicles in 2022. Similarly, the number of new motorbikes increased from 2,917,086 units in 2020 to 3,202,554 units in 2022. The average fuel consumption of vehicles with fewer than nine seats and an average engine displacement of 1,748 cc was 6.98 L/100 km during the 2016-2022 period, while the average fuel consumption of motorbikes was 1.96 L/100 km. By applying an annual reduction rate in fuel consumption of approximately 4%, based on current levels, and under GDP growth scenarios ranging from 8 to 11% (forecast for 2025-2030), the total reduction in CO₂ emissions is projected to range from 15.73 to 16.53 million tonnes. This reduction would meet the target set in Vietnam’s updated 2022 NDC.