Tạp chí Khoa học và Công nghệ Đại học Đà Nẵng

Design and experiment of independent Four-Wheel Drive system for electric vehicles

2025-11-10T15:08:43+07:00

This paper presents the design and experimental implementation of an independent Four-Wheel Drive (4WD) system for a low-speed electric vehicle, using four 350 W Brushless DC (BLDC) hub motors integrated directly into the wheels. Each motor is independently controlled by a PID controller and an Arduino Mega 2560 microcontroller, allowing precise speed regulation of each wheel. The speed feedback signals are obtained from the Hall sensors integrated within the motors, while the steering angle Encoder sensor and Hall-type throttle pedal sensor provide input data for calculating the reference speed of each wheel. Experimental results show that the PID controller implemented on the Arduino Mega 2560 is capable of effectively controlling the speed of all four wheels, ensuring stable vehicle operation. Although minor speed fluctuations occur due to load differences, the system responds well when transitioning from low to high speeds.

Effect of oxygen enrichment on syngas quality in small-scale downdraft gasification of RDF–rice husk

2025-12-22T18:50:31+07:00

This study investigates the impact of supplementing 20% oxygen into the air supply during the gasification of a 65% RDF and 35% rice husk blend in a small-scale downdraft gasifier. The results demonstrate that oxygen enrichment significantly elevates combustion zone temperatures and reduces nitrogen dilution, leading to a substantial increase in combustible gas components. Specifically, comparative data reveal that at an Air Ratio (ER) of 0.3, CO concentration rises markedly from 23% to 44%, resulting in a total combustible fraction of approximately 70%. Similarly, at ER 0.4, CO levels increase from 20% to 34%, while at ER 0.5, they rise from 12% to 30%. These findings confirm that oxygen enrichment effectively enhances the heating value and quality of biomass-derived syngas.

Indoor localization using transformer ensemble regression and LED signals

2025-12-30T11:06:26+07:00

Improving the localization accuracy under the influence of multipath reflections and signal interference in indoor localization systems using visible light signals remains a complex and challenging task. In this study, we propose utilizing the transformer architecture in a localization system based on light intensity signals of 16 LEDs. By leveraging the self-attention mechanism, the model can detect and focus on the locations with the highest relevance. The predictions are aggregated thanks to an ensemble strategy. Simulation results show that the proposed method achieves a Root Mean Square Error of approximately 0.334 m for the entire room (5x5 m), 0.14 m for the central region (3×3 m), and 0.39 m for the remaining areas near the walls and corners.

Micro-nanobubble technology in microalgae cultivation: a comprehensive overview

2025-12-23T16:01:14+07:00

Microalgae cultivation is currently constrained by two major techno-economic bottlenecks: poor gas-liquid mass transfer and high harvesting costs. This review examines micro-nanobubble (MNB) technology as a strategic solution to address these barriers. Owing to characteristics such as high internal pressure, prolonged residence time, and colloidal stability, MNBs significantly enhance the volumetric mass transfer coefficient ( ) while minimizing hydrodynamic shear stress. Case studies demonstrate that MNBs not only increase biomass productivity but also facilitate efficient flotation-based harvesting with low energy consumption (below 0.5 kWh·kg⁻¹ of dry biomass), while simultaneously improving nutrient removal in wastewater. Despite remaining challenges in scaling up, this technology offers a promising pathway for integration into circular economy models, driving the commercialization of microalgae for biofuels and high-value products.

Recovering a 4-DOF SCARA robot arm integrated with machine vision for real-time product classification

2025-12-15T08:59:25+07:00

This study proposes a real-time automated sorting solution by integrating a recovered 4-DOF robot arm with a machine-vision algorithm. The inverse kinematic computation is integrated in a PLC to control the robot arm. A QR code–based image processing method is used to decode product information, localize target positions, and transmit coordinates to the PLC for the sorting process. Experimental results confirm the successful recovery of the robot arm, achieving average positioning errors of 0.24 mm and 0.12 mm on the X- and Y-axes, respectively. The integrated system effectively classified and sorted three types of QR-labeled product boxes with an accuracy of 93.33% and
a processing time of 16 s per product. The proposed potential solution is entirely suitable for small and medium-sized enterprises.

Study on enhancing the efficiency of solar panels using condensate water recovered from air conditioner evaporator

2026-01-04T14:13:17+07:00

Under the tropical climate conditions of Ho Chi Minh City, the average ambient temperature of approximately 35.6°C causes the surface temperature of photovoltaic (PV) panels to gradually rise from 45°C ± 2°C under solar irradiance levels ranging from 800 to 1000 W/m², thereby reducing the system’s efficiency and durability. This study applies an active cooling solution using forced water spraying, in which domestic water (25–30°C) is mixed with condensate water from air-conditioning evaporator units (10–15°C) to produce a cooling source with a temperature range of 17.5–22.5°C. The experimental model shows that this method maintains a conversion efficiency of approximately η ≈ 19.5% to 20.08 and a power output close to the theoretical value, outperforming natural convection (~18.15%). The results demonstrate the feasibility of the mixed-water cooling system under hot and humid climatic conditions, contributing to improved energy harvesting efficiency and enhanced operational stability of the PV panels.

An RNN-based decoding scheme for IM/DD visible light communication systems

2025-12-30T11:11:35+07:00

In Visible Light Communication (VLC) systems, the integration of Forward Error Correction (FEC) and Run-Length Limited (RLL) coding is essential for ensuring transmission reliability and flicker-free operation. Despite their efficacy, traditional joint decoding schemes often suffer from prohibitive computational overhead. This paper introduces a Deep Learning-based decoding framework designed to replace the conventional concatenated RLL-FEC decoding chain. The proposed architecture employs a single-layer Recurrent Neural Network (RNN) followed by a dense fully-connected layer. Furthermore, a confidence-bit demodulation strategy is implemented to refine the input features for the RNN. Empirical results demonstrate that for short-packet scenarios, the proposed RNN-centric decoder achieves error-correction performance on par with state-of-the-art benchmarks while delivering a significant leap in processing throughput.

Evaluating municipal solid waste system and plastic waste leakage in Dong Ha City, Vietnam

2025-11-06T13:24:05+07:00

This study applied a waste flow diagram to clarify the status of municipal solid waste generation and waste flows, as well as model plastic waste leakage into the environment of Dong Ha City, Vietnam. Results denoted that the amount of municipal solid waste generation was about 0.66 kg/capita/day, being lower than estimated results of other Vietnamese cities. The majority of municipal solid waste generation was collected by formal collection service, at around 23,291 tonne/year, accounting for about 90% of total municipal solid waste generation. Around 5% of municipal solid waste (about 1,360 tonnes/year) was separated and recovered for recycling through the informal sector. Uncollected plastic waste (71%) and plastic waste leakage during collection and transportation (28%) were the two main sources contributing to plastic leakage. Thus, enhancement of the collection system plays the most important role in controlling plastic waste leakage.

Model-based design of a ballbot system controlled by mindstorms EV3

2025-11-10T15:12:20+07:00

Translating theoretical control principles into practical implementation remains a central challenge in control system engineering. Model-Based Design (MBD) has emerged as a crucial methodology to address this problem, especially when utilizing accessible platforms like LEGO Mindstorms EV3. This paper presents the MBD workflow for modeling and control of dynamic systems on the LEGO EV3 hardware, starting with DC motor position, speed control using a PID controller, and then advancing to a real-time balancing of a complex underactuated Ballbot system using an LQR controller. The MBD workflow includes system identification, model formulation, controller simulation, and tuning in MATLAB/Simulink, automatic code deployment to the EV3 brick and data acquisition for further analysis. Results show that this approach effectively reduces development effort, clarifies the link between theory and implementation, and highlights its broad applicability for systems of varying complexity, from simple motor control to advanced robotics.

On the L_p-convergence for compound random sums of pairwise independent random variables

2025-12-23T17:09:23+07:00

A random sum is the sum of a random number of random variables, and it has attracted much attention from many researchers. Compound random sums are extensions of classical random sums, in which the random index is determined by the partial sum of independent and identically distributed, non-negative integer-valued random variables. This paper establishes mean convergence theorems for compound random sums of pairwise independent (not necessarily identically distributed) random variables under the Cesàro uniform integrability condition. Our main results extend Theorem 3.1 of Giang and Hung [1] and Theorem 3.1 of Hung [2]. As immediate corollaries, we obtain weak laws of large numbers for negative-binomial sums of pairwise independent random variables.

Analysis of the reading passage difficulty and lexical demands in the Vietnamese high school graduation English tests (2015-2025)

2025-12-16T14:46:00+07:00

This study investigates the difficulty of the reading comprehension texts in the Vietnamese High School Graduation English Test (VGET), a matter of significant interest to various educational stakeholders. Twenty two passages from 2015 to 2025 were analyzed using classic readability formulas and lexical profiling. The findings suggest a potential misalignment between the measured text difficulty and the expected language proficiency level. This is supported by low reading ease scores (often below 50) and high lexical demand, requiring approximately 3,000-5,000 word families for 95% coverage. Texts with this level of difficulty may not be optimally suited for evaluating student graduation outcomes and could potentially create an excessive burden on test-takers. The study suggests that current test administration practices be reconsidered to ensure the test’s long-term validity and relevance. It also offers practical implications for both teachers and students adapting to the observed text complexity.

Cultural Intelligence and the theory of planned behavior in predicting work-abroad intentions: evidence from Vietnamese students in Australia

2025-08-01T10:32:40+07:00

This study integrates Cultural Intelligence (CQ) - specifically motivational and behavioral dimensions - with the Theory of Planned Behavior (TPB) to examine the intention to work abroad among Vietnamese students in Australia. Using data from 361 participants, analysis was conducted through SPSS 26 and SmartPLS 4.0 under a PLS-SEM framework. Results show that both TPB constructs and CQ components significantly influence work-abroad intention. Multicultural experience (MCE) significantly moderates the relationship between CQ and intention. Additionally, CQ moderates the effects of attitude and perceived behavioral control but not subjective norm. The study contributes theoretically by combining TPB and CQ into a unified model. Practical implications are proposed to support educational institutions and workforce development programs in preparing young talent for global employment.

Exploring mental health aspects of students at Vietnam national university, Ho Chi Minh City: current situation and policy implications

2026-01-16T15:35:53+07:00

This study examines the multidimensional nature of mental health among students at VNU-HCM through a questionnaire survey of 410 students. Three standardized psychological measurement instruments were employed: the Positive and Negative Affect Schedule (PANAS), the Depression Anxiety Stress Scales (DASS-21), and the General Health Questionnaire (GHQ-12). Data were collected online in May 2025 and analyzed using SPSS 25.0 with descriptive statistics and reliability testing. The results indicate that students reported relatively high levels of positive affect (PA: M = 31.74; SD = 7.46), while also exhibiting notable levels of stress, anxiety, and depression. The mean GHQ-12 score (M = 15.20; SD = 4.91) reflects a moderate level of psychological adjustment. The coexistence of positive and negative emotional states highlights the complexity of students’ psychological well-being, underscoring the need for a comprehensive approach to mental health support. The study recommends implementing systematic intervention programs to enhance students’ adaptive capacity and psychological resilience.

Exploring the relationship between logistics service quality in last-mile delivery and student satisfaction: a study at The University of Danang - University of Economics

2025-10-24T17:14:01+07:00

In recent years, Vietnam’s e-commerce has achieved strong growth, averaging over 18% per year during the 2018–2023 period and projected to reach US$52 billion by 2025. In this context, last-mile delivery is considered a decisive factor in the overall customer experience. This study aims to develop an integrated model to assess the impact of logistics service quality on student satisfaction with last-mile delivery services, based on a case study at The University of Danang - University of Economics. Through the integration of approaches from SERVQUAL and ACSI, the study proposes a research model suitable for the local context, emphasizing core components including delivery time, accuracy, responsiveness, and information quality. The study’s findings not only contribute to the theoretical foundation of logistics in emerging markets but also provide practical implications for businesses in meeting the increasingly high expectations of the young generation of customers.

Gendered pathways to purchase: modeling motivation, presence, and judgment in Vietnam’s online beauty and personal care sector

2025-11-10T23:37:44+07:00

This research proposes and empirically examines an integrated framework merging Self-Determination Theory (SDT) with the Throughput Model (TPM) to explain online purchase intentions in Vietnam’s beauty and personal care market. Focusing on Vietnam's online beauty sector, the research surveyed 323 young consumers to investigate the non-linear cognitive pathways influencing purchase intentions. Using PLS-SEM, the results confirmed a multi-pathway structure where Motivation, Presence, and Evaluation of Alternatives dynamically interact to shape Purchase Intention. Moreover, six distinct pathways within the context of online decision-making have been found to be significant. Crucially, a Multi-Group Analysis revealed significant gender differences: the relationships between Motivation and Presence, and Presence and Evaluation, are significantly stronger for women. These findings provide a nuanced, process-oriented understanding of digital consumer behavior, underscoring the necessity of gender-segmented e-commerce strategies.

Information technology capability, competitive advantage and bank profitability: evidence from Vietnamese commercial banks

2026-01-12T10:09:42+07:00

This study examines the impact of information and communication technology capability (ICT), bank competitive advantage (measured by market power LERNER index) and their interaction on the profitability of Vietnamese commercial banks. Using panel data from 31 banks between 2006 and 2022, the analysis applies the fixed-effect model with robust clustered standard errors. The results indicate that ICT capability and bank competitive advantage are both important determinants of bank profitability; however, their interaction reveals a long-term negative effect, indicating that ICT diminishes the profit advantage of banks with strong market power and that the marginal returns from ICT investment are lower for larger, more dominant banks compared to smaller ones. These findings contribute empirical evidence of how technology and market structure jointly shape financial performance of commerical banks in emerging markets. Policy implications highlight the need to optimize ICT strategies, promote fair competition and support digital transformation across different bank sizes.

The impact of religiosity on corporate debt structure

2026-01-13T10:24:13+07:00

This study examines the impact of religious beliefs on corporate debt structure using a regression model applied to a dataset comprising 485 firms across 10 countries over the period 2009–2022. The results indicate that, while firms operating in countries with higher levels of religiosity tend to rely more on long-term debt, religious beliefs do not have a significant effect on firms’ short-term debt decisions. In addition, we show that the positive effect of religiosity on long-term debt is less pronounced for firms with higher ratio of institutional ownership and more pronounced in countries with better control for the corruption. Our main findings remain robust when alternative measures of the dependent variable and alternative model specifications are employed. This study contributes to the literature on the relationship between religiosity and corporate debt structure, while also providing practical implications for other stakeholders.