Dong Thap University Journal of Science: Natural Sciences Issue

Studying some applications of the Lambert function in elementary mathematics

Vo Duc Thanh — 2026-03-03

This paper first introduces the Lambert function and discuss some of its fundamental properties. Next, it establishes a process for computing or approximating the value of the Lambert function at a given point. Furthermore, it presents several applications of the Lambert function in constructing and solving problems in elementary mathematics, including solving exponential equations and determining the limits of sequences. Finally, a collection of illustrative problems are provided to demonstrate these applications.

Coulomb drag in double bilayer graphene with inhomogenous background dielectric

Truong Van Oai — 2026-03-03

This paper presents the results of studying Coulomb drag resistivity in double bilayer graphene under the influence of an inhomogeneous substrate dielectric. Using the random phase approximation (RPA), this study determines the system's polarization function and the frequency-dependent dielectric function, thereby calculating the Coulomb drag resistivity. The results indicate that the Coulomb drag resistivity increases with increasing temperature but decreases rapidly as the interlayer distance between the bilayer graphene sheets increases. Notably, with an inhomogeneous background dielectric, the Coulomb drag resistivity is significantly higher than that in the case of a homogeneous dielectric. This phenomenon arises from the modification of the Coulomb interaction potential between electrons in the two layers due to the inhomogeneity of the background dielectric. Furthermore, calculations reveal that at different temperatures, the Coulomb drag resistivity tends to decrease with increasing carrier density. However, a distinct difference emerges between two cases: small and large interlayer separations. Under a small interlayer separation, the Coulomb drag resistivity is more strongly influenced by carrier density and temperature. These findings provide further insights into the role of the inhomogeneous background dielectric in double bilayer graphene systems and suggest potential applications for next-generation graphene-based electronic devices.

Spin-1 Ising model with biquadratic exchange interaction in an external magnetic field: A theoretical study within the mean-field approximation

Ngo Thi Thuan — 2026-03-03

The spin-1 Ising model with bilinear and biquadratic exchange interactions in an external magnetic field is studied on a simple two-dimensional square lattice within the mean-field approximation. The obtained results show the existence of dipolar or quadrupolar order, depending on the variation in the strength of the two types of interactions in the absence of a magnetic field. Furthermore, the influence of the external magnetic field on these order is also investigated in detail. These results are analyzed through the presence of spin-1 states with nonzero magnetic moment (i.e., S^z= \pm 1) and zero magnetic moment (i.e., S^z= 0).

Adsoption of voltatile organic compounds on activated carbon surface: a DFT study

Nguyen Ngoc Tri — 2026-03-03

In this work, the shapes of stable structures for organic compounds adsorption on activated carbon (AC) surface at pure- and Fe/Zn-doped states are obtained at the PBEPBE/6-31G(d) level of theory. The binding between sites of molecules and surface is focused on ring center and functional groups. For doped surfaces (Fe@AC, Zn@AC), the stable interactions are formed favorably at Fe/Zn sites and functional groups. The adsorption energy values of molecules on surfaces range from -6.2 to -8.3 kJ.mol^-1 for AC and from -7.4 to -49.3 kJ.mol^-1 for Zn@AC and -166.3 to -292.7 kJ.mol^-1 for Fe@AC. Noticeably, AIM and NBO results indicate the existence and strength of intermolecular interactions upon complexation. The H‧‧‧C*/π weak forces play an important role in the configuration strength for AC. Besides, the O‧‧‧Fe/Zn electrostatic interactions with partly covalent nature contribute significantly to the stability of configurations for Fe/Zn doped AC. The addition of Fe onto AC enhances the adsorption ability of organic molecules as compared to Zn-doping.

Cluster Isotherm Analysis and Quantum Structural Optimization of L-Proline on MKN-SWCNT S1 carbon nanotubes

Le Dinh Tuan — 2026-03-03

This study constructed the adsorption isotherm of L-proline on MKN-SWCNT S1 single-walled carbon nanotubes was constructed. The cluster adsorption model was used to analyze the experimental isotherm. The results showed that L-proline was adsorbed in the form of a monomer and a cluster composed of 6–7 monomers. Quantum chemical methods were used to optimize the structure and determine the basic parameters of the adsorption system. The results showed that the most likely mechanism for immobilizing amino acids on the carbon nanotube surface is Van der Waals interaction.

Optimization of waste paper pretreatment using response surface methodology for enhanced cellulose recovery efficiency

Nguyen Thanh Viet — 2026-03-03

This study focuses on optimizing the pretreatment process of waste cardboard using sodium hydroxide (NaOH) to recover high-purity cellulose for biological and industrial applications. Response Surface Methodology (RSM) combined with Central Composite Design (CCD) was used to investigate and optimize technological parameters, including NaOH concentration, temperature, treatment time, and the NaOH-to-paper ratio. A bleaching step using sodium hypochlorite (NaClO) was subsequently applied to improve cellulose purity. The optimal conditions were found at a temperature of 100°C, treatment time of 3.5 hours, 2.5% NaOH concentration, and a NaOH-to-paper ratio of 70/1 mL/g, resulting in a maximum impurity removal efficiency of 40.347%. The treated samples were characterized by field-emission scanning electron microscopy (FE-SEM) to observe surface morphology and Fourier-transform infrared spectroscopy (FTIR) to identify changes in chemical functional groups. This study contributes to enhancing paper recycling efficiency, minimizing solid waste, and promoting environmentally friendly and sustainable paper production processes. Recovered cellulose can be applied in the production of biofilms, biomedical materials, composite materials, or bio-adsorbent products, thereby increasing the utilization value of recycled materials and advancing the circular economy model.

Evaluating the ability to enrich the polyphenol content in the lotus seed epicarp extract by macroporous resin

Tran Trung Tinh — 2026-03-03

The lotus seed epicarp is a byproduct of lotus seed processing, mostly discarded or dried for use as fuel. Polyphenols, a group of compounds with antioxidant properties that protect cells from damage caused by free radicals, have been found in the lotus seed epicarp. An effective enrichment method is required to enhance the total polyphenol content in lotus seed epicarp extract while utilizing natural medicinal resources for disease prevention. Currently, macroporous resins have been much concerned due to their potential applications in the adsorption, isolation and purification of bioactive compounds such as phenolics, alkaloids, flavonoids, tannins, and saponins from plant extracts. With a simple implementation and operation process, low cost, avoidance of toxic solvents, and the ability to be reused, the enrichment of polyphenols using macroporous resins is considered a feasible and promising approach. This study evaluates several factors affecting the polyphenol enrichment process using macroporous resin. The results show that HPD 750 resin exhibits good adsorption and desorption capacities, with values of 18.96 0.16 mg/g and 68.56 1.28 %, respectively, under the following conditions: extract concentration of 5,000 ppm, adsorption time of 30 minutes, desorption solvent of 96% ethanol, and desorption time of 180 minutes. The polyphenol content in the extract before and after enrichment was determined to be 363.89 6.27 and 517.48 4.73 mg GAE/g. From these results, it can be concluded that the polyphenol enrichment method using macroporous resin is effective.

Study the effects of processing and packaging on the quality of gluten-free bread supplemented with breadfruit flour

Tran Thi Minh Thu — 2026-03-03

This study developed a gluten-free bread recipy from gluten-free ingredients such as breadfruit flour, rice flour, soybean flour, corn tarch, potato starch, sugar, yeast, butter, milk, salt, water, cooking oil, xanthan gum and maltodextrin. The effects of breadfruit flour supplementation (0%, 10%, 15%, and 20%), xanthan gum (0%, 0.5%, 0.7%, and 0.9%), butter (0%, 15%, 20%, and 25%), yeast (1.5%, 3%, and 4.5%), and fermentation time (30 minutes, 60 minutes, and 90 minutes) on several quality criterias of the bread were investigated. The results showed that supplementing with 15% breadfruit flour, 0.7% xanthan gum, 20% butter, 3% yeast, and fermenting for 60 minutes produced a product with a moisture content of 31.31%, hardness of 1.96 N, crust and crumb lightness (L*) of 50.83 and 59.51, crust and crumb yellowness of 20.27 and 5.17, fiber content of 1.92%, mineral content of 0.42%, and the highest sensory value. The product was stored in polypropylene (PP) packaging for 2 days showing acceptable microbial growth and retained relatively stable quality.

Research on modification of rubber wood (Hevea brasiliensis) using potassium silicate (K2SiO3)

Le Quynh Nhu — 2026-03-03

Potassium silicate (K₂SiO₃), also known as liquid glass, when used to treat wood, creates a series of physical changes in the wood structure that enhance moisture resistance, and thereby, it improves the physical properties of the wood. This experimental study evaluated the water absorption capacity and volumetric swelling rate of Rubberwood (Hevea brasiliensis) after treatment with potassium silicate (K₂SiO₃) over different treatment durations. The results showed the influence of these factors through the following regression correlation equations:Water absorption function: Y₁ = 54.9 – 10.21·x₁ – 0.7765·x₂ – 0.49·x₁·x₂ – 0.5979·x₁² + 1.2·x₂², Volumetric swelling rate function:Y₂ = 7.23 – 1.02·x₁ – 0.6936·x₂ + 0.265·x₁·x₂ + 0.2359·x₁² + 0.115·x₂² The optimal result for reducing water absorption in rubberwood was achieved with a potassium silicate concentration of X₁ = 1,414 (N = 27,07%) and a treatment duration of X₂ = 0.348 (T = 3,348 hours). Meanwhile, the optimal result for minimizing the volumetric swelling rate was identified at a potassium silicate concentration of X₁ = –0,43 (N = 17,85%) and a treatment duration of X₂ = 0,619 (T = 3,619 hours).

Effect of stocking density on growth and survival of Thai frogs (Rana tigerina) reared under antibiotic-free protocol

Nguyen Gia Hien — 2026-03-03

The study “Effect of stocking density on growth and survival of Thai frogs (Rana tigerina) reared under antibiotic-free protocol” was conducted over a period of 60 days. The objective of the study was to determine the appropriate stocking density of Rana tigerina to increase production per unit area without affecting growth, survival rate and feed efficiency of frogs. Frog with initial body weight of 8,0 g/frog were raised in a cement tank with an area of 2m² with 4 densities of 80, 100, 120 and 140 frog/m². Frog were fed twice a day at adlibitum rate with 30% protein pellet. No antibiotics were used during the experiment. Regularly supplement the biological product (Bacillus sp.) into the feed once a week to enhance the frogs' immunity, using a dosage of 3 g/kg of feed. During the experiment, any frog showing signs of illness will be isolated from the breeding tank. Research results showed that frogs raised using antibiotic-free processes at a stocking density of 100 frogs/m² gave the best results in terms of growth, survival rate, feed conversion ratio (FCR), and profitability. After 60 days of rearing, the average weight of the frogs was 155.6±6.42 g/frog, FCR was 1.14±0.02, the survival rate was 88.3±1.45% and the profit was 138,697 VND/m².