VNUHCM Journal of Engineering and Technology

Latest Articles

1. Research article

   The determination of the miss distance of artillery shells using the radio proximity fuse

   Quyền P.ạm

   The effectiveness of ammunition depends on many factors, of which the miss distance of artillery shells when using the radio proximity fuse utilizing the Doppler is one of the very important parameters when researching, designing, manufacturing fuses and directly affects the effect of artillery shells. Determining this parameter allows the selection of other technical parameters in the radio proximity fuse. This issue has always received the attention of many scientists, but so far, no specific research has been published. This paper presents the theoretical basis to determine the miss distance of artillery shells when using the radio proximity fuse utilizing the Doppler using analytical methods. Based on the target detection area and the fragment area, the article has shown the relationship between the miss distance of artillery shells, the warhead operating angle, and the phase of the miss distance. On that basis, the author has evaluated the change in the value of the miss distance of artillery shells when changing the warhead operating angle, the phase of the miss distance using Matlab software. The results have shown that the value of the miss distance of artillery shells depends significantly on the warhead operating angle, the phase of the miss distance, and the distance between the antenna position and the detonation position of the warhead. The results obtained can be applied to calculate and design the radio proximity fuse utilizing the Doppler effect for artillery shells to destroy aircrafts.

   Published: 2025-04-16In press
2. Research article

   Effect of drying aids concentration on the physicochemical properties of acerola powder producing by foam mat drying

   Duong D., Nguyen N., Hoang B.

   Acerola is known as a tropical fruit that is rich in health-beneficial biological compounds such as polyphenols and vitamin C. However, this raw material is susceptible to post-harvest damage due to its rapid ripening rate. Therefore, processing new products, such as soluble powder, is essential. The purpose of this study is to evaluate the impact of the addition rate of drying aids, including maltodextrin (8–12%) and hydroxylpropyl methylcellulose (0.75–1.25%), on the physicochemical properties of cherry powder. processed by the foam drying method. Research results show that changing the mixing ratio of drying aids affects the density and foaming, acid content, solubility, vitamin C, and polyphenols of the powder. In all samples with a maltodextrin addition rate of 12%, the sample had low foaming (<5%). Meanwhile, the remaining ratios have foaming levels of 80%–140%. The sample with the addition rate of 8% maltodextrin combined with 0.75% hydroxypropyl methylcellulose (HPMC) gave the finished product the highest values in terms of solubility, vitamin C content, and polyphenols. SEM scanning microphotograph results show that the powder has a flat morphology, no adhesion, an irregular shape, and a smooth surface. In addition, the PCA analysis results also show that the solubility, vitamin C content, and polyphenol content of the powder are positively correlated with foam expansion and negatively correlated with foam density. The resulting cherry powder can be used as a source of vitamin C.

   Published: 2025-04-15In press
3. Research article

   Simulation of CO2 sequestration in saline aquifers

   Tùng P.,ạm Bình N.ễn

   In recent years, global warming has become a serious issue in the petroleum industry and is continuously increasing over time. One of the key factors contributing to this situation is the accumulation of a large amount of Carbon Dioxide (CO2) in the atmosphere. Currently, to minimize the amount of CO2 in the atmosphere and address climate change, we need to consider effective methods for CO2 capture and storage; this is also a critical goal of Net Zero projects worldwide. In this study, the author constructed four CO2 storage models corresponding to four different trapping mechanisms, applied to the saline aquifer beneath the Meleiha oilfield in Egypt. The research was conducted with the support of three computer tools: Computer Modeling Group Ltd 2015, Techlog 2015, and Excel. The four trapping mechanisms include Structural trapping, which relies on geological structures to sequestration CO2, with the most important element being the caprock; residual gas trapping, which is based on capillary forces, was modeled by using Land's model; solubility trapping, which focuses on the dissolution of CO2 in saline water, and to clearly understand this mechanism, the author used the Peng-Robinson equation of state and Henry's law to simulate the processes involved; mineralization trapping involves CO2 reacting with components in saline water and mineral constituents present in rocks, and the author studied and used typical chemical equations to demonstrate the stable storage capacity of this trapping mechanism. The author assessed the contribution of each trapping mechanism to CO2 storage capacity and wellbore stability through pressure parameters.

   Published: 2024-12-31In press
4. Research article

   Easy and Efficient Patterning of Elastomer Dielectric toward Commercialization of Triboelectric Nanogenerator

   Bui T., Thu Ha L., Nguyen Hoang G., H., Luu T., A., Pham T., K., Tran V., K., La T. T. H.

   Triboelectric nanogenerators (TENGs) are an emerging technology for harnessing green energy and serving as essential power supply for self-charging mobile electronics. Achieving high electrical output in a cost-effective, large-scale production is crucial for the widespread practical application and commercialization of TENG, yet it remains significantly challenging. In this study, we present an innovative, scalable, and cost-effective approach for surface patterning of dielectric elastomer materials with the aim of advancing the commercial potential of TENG. Our method involves the preparation of a durable plastic mold featuring microwell-patterned surface (mw-plate mold), using plastic wastes such as disposal Petri dishes and CD discs, through a one-step dip-coating process. Subsequently, the convex-microbead-patterned polydimethylsiloxane (mb-PDMS) replicas are created using a micromolding technique. Our results indicate the superior structural integrity of the honeycomb mold throughout multiple molding processes, attributed to the reinforcing ability of the plastic plate. Furthermore, TENG device using mb-PDMS exhibit a remarkable average output power density of 3.92 mW×m^-2 with an open-circuit voltage (V_OC) of 185 V and a short-circuit current (I_SC) of 20 µA, representing a 5-fold increase over that of unstructured TENG, thereby demonstrating significantly enhanced electrification effectiveness through surface patterning. We believe that the convergence of cost-effective, scalable and efficient surface patterning of elastomer tribomaterials might enable new prospects for the commercialization of future TENGs for blue energy harvesting that requires a network of huge numbers of TENG devices.

   Published: 2024-12-31In press
5. Research article

   Study of the variation of drilling mud density with temperature, pressure, and circulation rate using artificial neural networks, statistical models, and empirical correlations

   Tùng P.,ạm Nhân N.ễn

   Well control is an important aspect of drilling operations because improper well control can result in kicks and blowouts with grave consequences. A successful well control requires a good understanding of the relationships between drilling mud pressure and formation pressure, as well as the variation of bottom hole pressure during drilling operations. As the hydrostatic pressure of the drilling mud column accounts for most of the pressure, a more accurate control of the changes of mud density will contribute to a more accurate bottom hole pressure modeling. Regarding the control of the mud density, a practical problem has existed so far in petroleum drilling: the mud density is determined at the surface condition, and its values vary along the depth of the well because of the changes of temperature and pressure, which consequently leads to an inaccuracy in mud density control in reality.

   Published: 2024-12-31In press
6. Research article

   Optimization Design and Experimental Evaluation of a Low-Cost Linear Motor with Compliant Bearings for Precision Engineering Applications

   Phạm T.,ấn Le A., Le N., Nguyen T.

   This paper presents the structural optimization and experimental evaluation of a novel linear motor for applications in precision engineering industry. The output linear motion from the motor is supposed to be highly accurate since it is supported by a couple of compliant bearings. The stroke of the proposed motor is determined by the largest displacement of compliant bearings in elastic region. Therefore, the beam-type flexure, which is able to produce large elastic deformation, is suitable for the compliant bearing design. In addition, the bearing design is optimized using the response surface methodology (RSM) in ANSYS to achieve a compliant structure with high deformation capability in desired directions. The optimized bearings will then be assembled with the voice coil actuator (VCA) to create a complete 1-DOF linear motor. Several experimental evaluations are carried out to verify the actual performance of the motor. The experimental results suggest that the proposed linear motor is able to produce precise linear motion with high accuracy and high repeatability. Furthermore, the millimeter-scale stroke of the motor is large enough to use in a variety of devices in precision engineering industry.

   Published: 2024-12-31In press
7. Research article

   A passivity-based neural control using genetic algorithm for a DC-DC boost power converter

   Huỳnh M., N.,ọc Duong H., N., Nguyen V. H.

   In this paper, a passivity – based neural control using genetic algorithm of a DC-DC boost power converter is proposed. The output of a DC-DC boost power converter is an inductor current. The control input is the duty ratio. Using a co-ordinate transformation of state variables and control input, a DC-DC boost power converter is passive. A new plant is zero-state observable and the equilibrium point at origin of this plant is asymptotically stable. A passivity - based control law is constructed by using neural network. The goal is that the capacitor voltage is equal to the desired voltage. The neural network has three layers: the input layer, the hidden layer and the output layer. The activation function of the hidden layer is tangent-hyperbolic and the activation of the output layer is linear. The weights of neural network are also adjusted optimally by genetic algorithm using decimal encoder. The general algorithm of neural network for a passivity-based control is also constructed. Simulation results are done with Simulink in MATLAB. Simulation results of the passivity-based neural control without using genetic algorithm are good and show that the capacitor voltage v is kept at the desired voltage V_d when the input voltage E and the load resistor R vary. Further, the simulation results of the passivity – based neural control using genetic algorithm have good performance such as short settling time, 3 ms and small steady-state error, which is indicated by IAE (integral absolute error (IAE) of the desired voltage and the capacitor voltage), 0.0343.  The results of passivity-based neural control using genetic algorithm shows that the capacitor voltage is kept at the desired value V_d. Finally, simulation results show that the passivity-based neural control using genetic algorithm is better than the passivity-based neural control.

   Published: 2024-12-31In press
8. Research article

   Voltage and Frequency controller for parallel Inverters in Microgrid using Fuzzy logic

   Pham X. H.

   The inverters in Microgrid are connected in parallel to improve efficiency, increase transmission capacity, and easy to repair and maintain. When the Microgrid is operating in standalone mode, the inverters must be controlled to share their power according to the rated ratio, this is to stabilize the frequency and voltage in the Microgrid. The droop control method for power control for parallel-connected inverters is one of the most popular power-sharing methods today, some studies have presented traditional and improved droop control methods. However, the purpose of the studies is power-sharing for the inverters that no purpose of reducing the voltage and frequency deviation to improve power quality. This paper is shown the adjusting of the voltage and frequency method based on fuzzy logic with an aim is minimize the voltage and frequency deviation for improving power quality in Microgrid. This controller consists of a Droop combined with fuzzy logic to control changes in the slope of the power curve when the load changes, thereby the voltage and frequency deviation could be adjusted. This control method is called the Droop-fuzzy logic control method. Experimental results confirm the validity of the proposed control. Simulation and experimental results will prove the effectiveness of the proposed method.

   Published: 2024-12-31In press
9. Research article

   Power Control of Parallel Inverters in Microgrid

   Pham X. H.

   In Microgrid, inverters are connected in parallel to improve efficiency, increase transmission capacity, easily repair, maintain, and facilitate Microgrid structure change. However, in stand-alone mode the inverters must be controlled to power-sharing by the ratio of their rated power, because if the current supplied to the load is not be shared by the ratio of the rated power of the inverters, it will be a guide to an overload, or reactive current circulating in the inverters, which will lead to heating and even damage to the inverters. Therefore in this paper also introduces a power-sharing control method for parallel-connected inverters in the Microgrid. The proposed controller will perform the correct power sharing according to the rated power ratio of the inverters connected in parallel in Microgrid, this controller is not affected by line impedance and local loads under usual or where field cases communication bus combination is delayed or interrupted.

   Published: 2024-12-31In press
10. Research article

    A general mathematical model to determine temperature and moisture distributions in drying of spherical products: case studies of green peas, barley, and cranberry

    Thao P., B., Truyen D., C., Phu N. M.

    Forced convection drying is a simple and effective dehydration method widely applied in post-harvest technology. Sphere-shaped materials account for a large proportion compared to other shapes. Therefore, this study forms a general mathematical model and resolution method to predict the temperature and moisture content of spherical drying materials with time. Three representative spheres of green peas, cranberries, and barley were used as case studies to validate the simulation results with experimental results. All three crops are widely used in cooking. Green peas are often used in stews, salads or processed into soybeans. Cranberries are frequently employed in desserts, juices or processed into jam. Barley is often used to make bread and beer and is also an important grain source in human nutrition. The Arrhenius model predicts the moisture diffusion coefficient with temperature to link the temperature and moisture equations, and they are solved simultaneously. In drying applications, the Arrhenius model is often utilized to describe the temperature dependence of moisture diffusion coefficients or drying rates. By applying the Arrhenius equation to drying kinetics, the relationship between drying rate and temperature can be quantified, allowing for the prediction and optimization of drying processes under different temperature conditions. These three objects have very different input parameters to illustrate the wide applicability of the proposed solution method. The results show that there is a large difference in moisture content at the center and surface of a crop. On the contrary, the temperature is evenly distributed, and the dried object quickly reaches the drying air temperature. The laws of heat transfer and moisture transfer are analogy. However, the moisture diffusion coefficient and moisture transfer coefficient are much smaller than the thermal diffusion coefficient and heat transfer coefficient.

    Published: 2024-12-31In press