VNUHCM Journal of Engineering and Technology

Research and Develop the Motion Controller in the Mechanical Servo System

Minh Tuan Nguyen — 2023-10-16

In the field of mechanical engineering, the precision and real-time of high-performance manufacturing machine plays an important role. Recently, some solutions for servo system could overcome these drawbacks. Therefore, a design of motion controller to manipulate the highly precise position control and stability. The investigation of both hardware design and software programming is presented in this work. In addition, overall system is created in the real-world application. The use of the seven segments polynomial in motion generator provides an intuitive examination. From these results, it is clarified that the effectiveness and feasibility of our design and control is proper for industrial applications

In vitro and in vivo antifungal activity of extracts from Jamaica cherry Muntingia calabura l. leaves

Nguyen Hoang Phuc Nguyen — 2023-10-16

Previous studies on M. calabura (Jamaica cherry) leaves reported the presence of polyphenols, flavonoids, glycosides, and tannins. However, the deep research focus on the antifungal activity of Jamaica cherry leaf extract (JCLE) is still limited. Hence, the current study was conducted on JCLE samples by using various solvents, i.e., 70% ethanol, 70% methanol, and 70% acetone, and then evaluating their antifungal activity. Analytical results showed that JCLE could be used as a natural antifungal potential agent against mold-causing spoilage in fruits. Specifically, the ethanolic extract had a strong inhibition of Colletotrichum gloeosporioides and Lasiodiplodia theobromae. While the methanolic and acetonic extracts prevented sharply the growth of Alternaria alternata and Fusarium equiseti, respectively. Generally, the ethanolic extract was able to inhibit the various mold strains better than the other solvents. Furthermore, the results showed that the percentage inhibition of radial growth (PIRG) of JCLE increased gradually as the concentration increased from 4000 to 40000 mg GAE/kg. The highest data obtained for C. gloeosporioides, A. alternata, F. equiseti, and L. theobromae were 53.29%, 57.03%, 54.81%, and 75.03%, respectively. In vivo experiment, the samples were treated with and without JCLE (the control sample) occuring the black spots caused by C. gloeosporioides on mango’s surface after 21 days and 30 days of storage at 12 ± 2 °C, respectively. Whereas the TSS and TA values of both samples were similar. While the visual appearance of the control was more yellow compared to the samples treated with JCLE. In conclusion, JCLE was able to significantly delay the development of pathogenic mold, though it quite inhibited the maturation of mango fruit. Further studies may be needed to evaluate the phtychemical profile of M. calabura extract to gain a deeper understanding of its antifugal activity.

Accelerating the nonlinear analysis of hyper-elastic behavior by GMDH-assisted Newton-Raphson scheme

Minh Ngoc Nguyen — 2023-10-16

This paper presents an accelerated iterative scheme for nonlinear problems. Commonly, analysis of nonlinear behavior is conducted by the Newton-Raphson (NR) method. It is well-known that the number of iterations required depends on the deviation between the “starting point” and the converged solution. In practice, the solution of previous load step is taken as the “starting point”, while the converged solution of the current load step is not known beforehand. Therefore, difficulties or even non-convergence may occur. Recently, it is suggested that a neural network is employed to predict the solution of the current load step. This prediction is then used as the “starting point” for NR scheme. It is expected, that the true converged solution (of current step) is closer to the prediction by neural network than to the solution of previous load step. As a result, the scheme becomes faster due to less iterations. Obviously, any techniques for time-series forecasting can be used. Here, the Group Method of Data Handling (GMDH) is proposed. Loosely speaking, GMDH is a feedforward neural network without backpropagation. Practically, the GMDH-assisted NR scheme should not take longer time than conventional NR scheme. The advantage of GMDH is fast computation; however, the accuracy may be not as high as a network that has backpropagation. Therefore, careful consideration on the construction of GMDH network is needed. In the current work, the performance of GMDH-assisted NR scheme is investigated in analysis of hyper-elastic behavior, which involves both geometrical and material nonlinearity. A study on the influence of activation function on the accuracy is presented. Also, it is found that prediction for incremental displacement (between the current load step and the previous load step) could be better than prediction of displacement of the current load step.

Effect of sugarcane bagasse ash on compressive strength and water absorption of foam concrete using sea sand and seawater

Vu Quang Thuan — 2023-10-16

The rapid development of infrastructure has led to a shortage of construction materials. Therefore, the utilization of waste or potential materials is gaining attention. This study aims to investigate the effect of partially replacing Portland cement with sugarcane bagasse ash (SCBA) in Phu Yen province and sea sand-seawater (SSSW) on the properties of foam concrete. Portland cement was replaced with SCBA at 0, 5, 10, and 15% by mass of the binder. The results showed that the compressive strength of foam concrete was reduced at 7 days due to the SCBA replacement. However, the inclusion of 5% and 10% SCBA increased the compressive strength and reduced the water absorption of foam concrete compared to the reference concrete at 91 days. Moreover, the combination of SCBA and SSSW significantly contributed to the enhancement of compressive strength and reduction of water absorption of foam concrete at 91 days, especially when SCBA replacement was less than 10%. In general, the use of SCBA and SSSW is feasible in the production of foam concrete, considering the increasing scarcity of construction materials and the goal of reducing CO2 emissions.

A Search Group Algorithm for Optimal Distributed Generation Placement

Truong Hoang Bao Huy — 2023-10-19

The integration of renewable-based distributed generation (DG) in distribution networks is increasingly common worldwide due to fossil fuel depletion, environmental pollution, and global warming. This paper proposes a Search Group Algorithm (SGA) method to determine the optimal location, capacity, and quantity of DGs in distribution networks. The SGA method has a good ability to find optimal solutions thanks to the ability to balance between the global search and local search in the optimization process. The objective of the problem is to minimize the power loss of the distribution networks while meeting the constraints of the networks, such as power balance, bus voltage limit, branch current limit, DG power limit, and DG penetration limit. The proposed method is applied to the IEEE 33-node and 69-node distribution networks with two different cases. After integrating DGs into distribution networks, the power loss are reduced by 70.14% and 70.23% for the 33-node and 69-node distribution networks, respectively. The results obtained from the SGA method were compared with other methods in the literature. The simulation results have proved that the SGA method has good performance for the optimal DG placement problem in distribution networks.

Towards formal verification of smart grids: An effective modelling approach and some first experimentation

Tuan Cong Bui — 2023-10-24

Nowadays, smart grids are used widely around the world when they enable detecting, reacting and pro-acting to changes in usage and many concerns with the power system, as well as having self-healing capabilities. Some smart grids have recently been created and operational in Vietnam. To ensure the effectiveness of the smart grids, the correctness of the system designs must be studied carefully before the explosion of the use of smart grids, particularly in developing countries such as Vietnam. As formal methods, including formal verification and model checking, recently play more important role in verifying smart grid properties such as load balancing and fault resilience, the effectiveness of formal verification depends mostly on system modeling and verification techniques. Recent researches have shown the feasibility of applying model-checking tools in smart grid verification, and also the inability to test complex properties and systems. In our opinion, the inability could be come from the complicating of the models of the system-under-test. In this study, we suggested a new method for representing smart grids using Colored Petri Net (CPN), a formal representa- tion language. In comparing to the current modeling approach, the new model allows engineers transforms complex grids into simple models. Moreover, based on the advantages of the “color” aspect of the CPN, the result model can be easily upgraded to adapt to the changes of the original smart grids without re- modeling. Also in this study, a basic case study for representing a smart grid, which consists of multiple power sources and multiple consumers, will be shown. The model will be configured to capture some problems that may happen in the grid such as the changing of the capacity of the power sources. The verification experimentation conducted on the case study shows the usefulness of the proposed method.

Frying of sliced shallot (Allium ascalonium): Product quality and kinetic models at different frying temperatures

Hoang Minh Quang Le — 2023-10-24

Shallot (Allium ascalonium) is a popular ingredient in Asian cuisine including Vietnam. Fried shallot is widely used in the preparation of various traditional meals. However, the kinetic models of sliced shallot frying process have not been considered. In this study, the effects of frying temperature on changes in moisture content, oil uptake, hardness and instrumental color of sliced shallot were examined and their kinetic models were investigated. Increase in frying temperature from 130 to 150oC accelerated the moisture loss and oil uptake content of the shallot in order to achieve the equilibrium values within a shorter frying time. At the frying temperature of 130, 140 and 150oC, the final moisture content of fried shallot was 2.60 ± 0.36, 2.92 ± 0.35 and 1.64 ± 0.43 g/100g, while the oil uptake content was 47.26 ± 1.42, 46.36 ± 1.45 and 46.07 ± 0.40 g/100g dry matter, respectively. During the first step of frying, the hardness of shallot was slightly reduced but it was greatly enhanced and achieved maximum at the end of the process. In addition, the darkness level of fried shallot witnessed the same upward trend during frying. Based on the experimental data, the appropriate kinetic models for changes in moisture content, oil uptake level, hardness and color values of sliced shallot during the frying process at different temperatures were being developed with the correlation (R2) larger than 0.95. Page model appeared to be the most appropriate for moisture loss and oil uptake whilst the three models including Newton model, Wang & Singh model, Third-order Polynomial model were shown to be suitable for changes in hardness of fried shallot. However, the changes in color values only fit the Third-order Polynomial model. In conclusion, this study could predict the effects of temperature and time on the shallot quality during the frying process.

Effect of mixing phenol/rice husk to the ability form phenolic resin

Dieu Hanh Ong — 2023-11-12

Rice is an essential plant that brings high economic value to Viet Nam. In addition to the main product, rice agriculture produces a significant amount of by-products each year. This waste is known as rice husk. The amount of rice husks discharged each year is estimated to be over 9 million tons. They are usually processed by burning. Another amount is released into the environment. These treatments are potentially harmful to the environment and bring low economic efficiency. Therefore, many ways of treatment were suggested and considered. In this study, rice husk was used to synthesize phenolic resin. The rice husk was ground to powder less than 500μm. The husk powder, phenol, and sulfuric acid were mixed with different ratios. The mixtures were heated to 150℃ and soaked for 180 minutes. The efficiency of the reaction was evaluated through the remaining amount of rice husk. The C13 Nuclear Magnetic Resonance Spectroscopy (C13 - NMR) and Fourier Transform Infrared Spectroscopy (FTIR) were used to determine the structure and functional groups of the resin. A number average molecular weight (Mn) and a weight average molecular weight (Mw) were defined by using Gel Permeation Chromatography (GPC). The results show that phenolic resin was synthesized successfully from rice husk. The optimal ratio between phenol and rice husk powder is 2:1 with a 5% sulfuric acid additive. The efficiency of the reaction is determined at 90.34%. The results of structure prediction by FTIR and C13 - NMR show that the molecular formula of the formed resin is (CH2 - C6H4 - OH)n. It has the weight average molecular weight value of 11709 and the number average molecular weight of 7782. The synthesized phenolic resin can be applied as a binder or as one kind of heat-resistant plastic.

The influence of fluid-structure interactions 2-ways on dynamic characteristics of flexible tank

Bui Pham Duc Tuong — 2023-12-07

This paper investigates the influence of two-way fluid-structure interactions (FSI) on the dynamic characteristics of flexible storage liquid tanks. A coupled finite volume method FVM and finite element method FEM (FVM/FEM) was developed to simulate a flexible water tank subjected to seismic loading. FVM is used to simulate the fluid domain and FEM is used to capture the structural domain. The two-dimensional interaction equation is solved at the contact surface between the elastic tank wall and the fluid by tuning the relaxation parameter and convergence conditions. The model investigates the influence of considering two-way FSI on the dynamic characteristics of a tank flexible to a rigid tank wall. The results show that the frequency of flexible tank walls differs from that of rigid walls, especially the hydrodynamic pressure of liquid motion acting on the tank. A “threshold value” is revealed to distinguish flexible or rigid tanks. If the tank stiffness exceeds this threshold, then the thicker the tank is, the lower the hydrodynamic pressure. However, if the tank stiffness is less than this threshold, the thinner the tank is, the lower the hydrodynamic pressure. Further experiments on a fluid container under harmonic excitation are carried out using a shaking table to verify the dynamic behavior in comparison to numerical results. Good agreement is observed between numerical, analytical, published, and experimental data.

Screening for in vitro inhibiting Nrf2 of some Vietnamese medicinal plants

Hien Minh Nguyen — 2023-12-07

Nuclear factor erythroid 2–related factor 2 (Nrf2) is vital in regulating cellular defenses against oxidative or environmental aggressors. Some studies reveal that increasing Nrf2 activity affects chemotherapy drug resistance in cancer; thus, Nrf2 has become an attractive target in cancer therapeutics research. Our study screened the effects of 52 methanol extracts from different parts of 24 medicinal plants used in traditional and folk medicine to evaluate the ability to inhibit Nrf2 and the cell viability by an in vitro model of Huh7 liver cancer cells at the crude extract concentration of 100 µg/mL. The study has successfully suggested a screening model for Nrf2 expression based on luciferase fluorescence assay of Huh7 cells transfected with the Nrf2 gene. The results of our study show that the Piper sarmentosum roots can inhibit nearly 90% of Nrf2 activity in cancer cells. We also found that the extracts of Vernonia amygdalina leaves, Phyllanthus amarus leaves, Zingiber zerumbet leaves, Hyptis suaveolens leaves and roots, Curcuma zedoaria leaves and roots, Luvunga scandens leaves, Helicteres hirsuta leaves, Oroxylum indicum stem and leaves, Lasia spinosa fruits and Crotalaria pallida leaves inhibited more than 60% of Nrf2 expression levels. Furthermore, the extracts from the leaves of Luvunga scandens and Curcuma zedoaria can cause toxicity on cancer cell of more than 70% at 100 µg/mL. From the study, we have the basis for further studies on natural active substances that have the effect of drug resistance by inhibiting the expression of Nrf2 on cancer cells.