Tạp chí Khoa học Trường Đại học Vinh

A mean convergence theorem for triangular arrays of rowwise and pairwise mn -dependent random variables

Le Van Thanh, Pham Nhu Y — Fri, 08 Mar 2024 10:57:42 +0700

This paper establishes a mean convergence theorem for triangular arrays of rowwise and pairwise m_n-dependent random variables. Some authors studied limit theorems for sequences of pairwise m-dependent random variables where m is fixed (see, e.g., Quang and Nguyen [Applications of Mathematics, 2016] and Thanh [Bulletin of the Institute of Mathematics Academia Sinica, 2005]). In this paper, we establish a limit theorem for triangular arrays of rowwise and pairwise m_n-dependent random variables, where m_n may approach infinity as n → ∞. The main theorem extends some results in the literature, including Theorem 3.1 of Chen, Bai and Sung in [Journal of Mathematical Analysis and Applications, 2014].

Evaluation of the growth, yield and quality of Rehmannia glutinosa (DH19) in the midland and mountainous region of Nothern Vietnam

Pham Thanh Loan, Hoang Thi Le Thu — Fri, 08 Mar 2024 10:58:13 +0700

The study aimed to determine the growth performance and plant adaptation of R. glutinosa (DH19) to the selected plantation locations in Vietnam's Northern Midland and Mountainous regions. The experiments were arranged in a completely randomized block design and performed on three sites in Vinh Phuc, Phu Tho, and Tuyen Quang provinces. Research showed that DH19 was grown and developed well, gaining an average yield of 23.9 to 24.8 tons/ha and the catalpol content from 0.72 - 0.74%. DH19 was adapted to moderate drought conditions but severely damaged and recovered poorly in flooding. Planting DH19 should pay attention to root sores disease (Rhizoctonia solani) at the seedling stage and root rot disease (Fusarium sp.) at the harvest stage. The above study results show that DH19 can be selected for planting in Vietnam's Northern Midland and Mountainous regions.

Assessment of water resource variation in the lam river basin from 1970 to 2022

Nguyen Xuan Tien, Le Tien Huu, Ho Thi Phuong, Nguyen Van Lam — Fri, 08 Mar 2024 10:58:57 +0700

The purpose of this research is to examine the change in water resources over the previous 50 years in the Lam River basin (also known as the Ca River) in Nghe An province, an important water resource basin in the North Central area. According to the findings, the amount of flow through hydrological stations on rivers and streams in Nghe An province has been falling since 2012, and the yearly flow pattern is continuously dropping. For many years following 2015, the flow has been lower than typical, owing to the drought that occurred during the dry season of 2015-2016.

A simple design of broadband cross-polarization converter for the THz frequency range

Nguyen Thi Minh el al. — Fri, 08 Mar 2024 10:59:53 +0700

A broadband and lightweight polarization converter is proposed for applications in the THz frequency region. The proposed design has a metasurface structure with the dielectric layer modified to a hollow structure to obtain a lightweight design. The unit cell consists of two opposite arcs resonator patches and a continuous metal patch separated by the polyimide substrate layer. The simulated results indicate that the proposed polarized converter achieves a polarization conversion ratio above 93% in the frequency range from 1.6 THz to 5.8 THz with a relative bandwidth of 113.5%.

Designing an automatic beverage mixing system based on the Internet of Things.

Hoang Thi Phuong — Fri, 08 Mar 2024 11:00:13 +0700

This paper focuses on the research and development of an automated beverage mixing system. By applying modern Internet of Things (IoT) technology and information technology, the system incorporates intelligent functions such as touch sensing, internet connectivity, and beverage dispenser control software. It can provide a wide variety of high-quality beverages, including coffee, tea, juices, alcoholic drinks, and drinks made with syrups, sugar and milk. The advantages of this beverage dispenser include cost-effectiveness in installation, reduced labor requirements, compact size for versatile placement, and the ability to meet customer demands conveniently and flexibly. Results from practical testing demonstrate the stable operation of the machine, accurately following the pre-programmed beverage mixing instructions. The product can be used in real-world settings such as cafes, households, or office spaces.

Developing a supportive device for wrist injury rehabilitation training

Dien Thi Hong Ha — Fri, 08 Mar 2024 11:00:45 +0700

In this paper, we develop a supportive device to monitor the rehabilitation exercise process for people with disabilities to use their hands. The prototype is designed to include a resistance cable system to support the rehabilitation of the patient's hand motor function. During training, the patient pulls the resistance cable to exercise, and the resistance cable system applies force to the product's sensor block. The sensor block is capable of measuring parameters when force is applied, allowing the calculation of hand force during the patient's training. The hand force data obtained from the sensor block is then sent to a separate IoT-based application. This mobile-platform app is particularly developed for hosting data and providing a view for user to track his/her process of training. Additionally, the product is designed with angle measurement capabilities to track motion coordinates during the patient's hand training. The product is tailored to the physique of Vietnamese individuals. The patient's training results are stored on the Internet and displayed on a mobile application, facilitating the monitoring of training progress, comparing patient training results with standard data, and allowing remote monitoring by the patient's family members or healthcare professionals.

Application of natural-based anti-fungal formulations for bamboo and wooden household products

Le Thi My Chau el al. — Fri, 08 Mar 2024 11:01:21 +0700

This paper is concerned with the ability of natural products such as vinegar, tea, okra, lemon juice, grapefruit peel essential oil, and baking soda to prevent mold growth on bamboo and wood materials. The results showed that grapefruit peel essential oil had the highest biological activity compared to the other products in preventing mold growth on wood materials. Additionally, a process for preventing mold growth on bamboo and wood materials was developed and the parameters were optimized using the Box-Behnken surface response correlation method. The optimal process conditions were determined by analyzing the response surface of the three-dimensional surface plot and solving the regression model equation using Design Expert software. The optimal conditions, including the ratio of product to coverage area 5/1, concentration 53%, time in 238 minutes and temperature , have been tested and showed that the time for mold appearance was 254 days.

Regular activities of adult Ptyas mucosa (Linnaeus, 1758) in a farming conditions of Nghe An province, Viet Nam

Ong Vinh An, Dang Huy Huynh, Hoang Xuan Quang, Tran Kien — Fri, 08 Mar 2024 11:01:53 +0700

In the feeding condition in Cua Lo Town, Nghe An province, Viet Nam, adult Ptyas mucosa (P. mucosa) operates seasonally and day and night with the rule: The active season is from March to December and hibernating in January and February every year. For the rule of day and night operation: In March and April, they are mainly active from 6-18h; from May to July, they are operates at the 2 time periods: 7-11h (at most 8-10h), and 15-20h; In August, they are also operates 2 time periods, but from 5-11h, and 14 - 20h; From September to December, it operates at one period (6 or 7-19h), not active at night. The activity of adult P. mucosa is closely dependent on the temperature and humidity of the environment (20-40^oC, 40-100%), the most favorable is 27-31^oC, 76-92%. They officially hibernate in January and February when the ambient temperature is below 17^oC for many days.

Antimicrobio activity of esential oils from leaf of Syzygium tsoongii (Merr.) Merr. & Perry, Syzygium bullockii (hance) Merr. & Perry and Syzygium zeylanicum (L.) dc. in Ha Tinh Province

Tran Hau Khanh — Fri, 08 Mar 2024 11:02:31 +0700

Research on antimicrobial activity of essential oils from leaf of Syzygium tsoongii, Syzygium bullockii and Syzygium zeylanicum in Ha Tinh Province showed that essential oils from leaves of three species had antibacterial activity against three strains on the Gram (+): (Enterococus faecalis (ATCC 299212), Staphylococcus aureus (ATCC 25923), Bacillus cereus (ATCC 14579) and against Candida albicans (ATCC 10231). The essential oil from the leaves of Syzygium tsoongii and Syzygium zeylanicum had not antibacterial activity against Gram (-), while the essential oil from the leaves of Syzygium bullockii could be against 2 strains of Gram (-): Escherichia coli and Salmonella enterica strains.

Researching and developing a smart lock system applying artificial intelligence

Tran Thi Hien, Dao Thi Hang, Pham Van Phi — Fri, 08 Mar 2024 11:02:55 +0700

This paper focuses on researching and developing a smart security lock system using artificial intelligence, specifically facial recognition technology combined with the Internet of Things (IoT) to automatically recognize faces of accessing people.. The system is constructed with both hardware and software components, designed to verify the correct face stored in the database. The results show a high practical application potential, meeting the designed hardware and system programming objectives. The product can be used as an access control system based on facial recognition for government offices or industrial areas. Its advantages include cardless attendance tracking, fast and accurate verification, cost-effective installation, energy efficiency, compactness, and high efficiency.

Biomass production of algae Nannochloropsis oculata at large scale in Quynh Luu distric, Nghe An province

Chu Chi Thiet et al. — Fri, 08 Mar 2024 11:03:55 +0700

The research was conducted to complete technological protocol of biomass production of algae Nannochloropsis oculata with both culture methods in plastic bags and photo-bioreactor systems. The results show that in the nylon bag system, algae reached a peak of biomass density at day-8 of culture with 80 million cells per ml. In the photo-bioreactor systems, algae were higher density (180 million cells per ml), and longer period of culture (15 days of culture) than in plastic bags. The total products of 404.4 kg of fresh concetrated algae and 57.6 kg of dried algae powder which were suitable produced under climate conditions in Nghe An. All the algae products met the quality and requirements for use as food for aquatic animals as well as raw materials for the production of functional foods for humans.

Influence of spontaneously generated coherence and related phase on an all-optical switching in a three-level ladder-type system with incoherent pumping

Fri, 08 Mar 2024 11:04:29 +0700

This paper investigates the impact of spontaneously generated coherence (SGC) and relative phase on the propagation of a probe laser pulse in the presence of an incoherent pump field. It was discovered that when the control laser field is turned on, the medium forms an electromagnetically induced transparency (EIT) effect. Hence, the propagation of the probe laser pulse has a like-soliton form/shape. On the contrary, the probe laser field is rapidly attenuated when the control laser field is turned off. This feature allows the creation of a mechanism to turn “off” and “on” the probe laser field through “turning off” and “on” the control laser field, i.e., an all-optical switching mechanism based on EIT. Besides intensity and frequency, the laser field is also characterized by polarization and phase. The EIT has the nature of quantum interference, so it is very sensitive to changes in polarization, especially in the presence of relative phase between laser fields. Therefore, they also significantly affect pulse propagation and optical switching performance. The research results could be helpful for experimental observations or applications in photonic devices such as logic gates, quantum optical information processors, and quantum computers.

Realization of 650 nm fiber-coupled diode lasers module with output beam redirection for application in phototherapy and photodynamic inactivation of bacterials

Nguyen Thanh Phuong et al. — Fri, 08 Mar 2024 11:05:52 +0700

Currently, diode lasers in the red wavelength region, especially at 650 nm, are extensively utilized in phototherapy and photodynamic inactivation of bacterials by numerous research groups in the field of lasers for biomedical application. These devices offer exceptional advantages, such as their compact size, ease of design and integration, user-friendliness, and high safety for both operators and patients. Among these, fiber-coupled diode lasers provide an efficient solution for delivering radiation from the laser chip to the desired location. However, further optimization is still required for the fabrication technological development of these devices to meet specific application needs. This includes aspects like reducing manufacturing costs, improving component usability during operation, and meeting specialized usage requirements. To develop the technology for device fabrication, addressing the aforementioned demands, we conducted research on the design, fabrication, and characterization of fiber-coupled semiconductor lasers operating at a wavelength of 650 nm. The characterization results demonstrate that the manufactured devices can operate at maximal pumping current of 100 mA and under varying temperatures from 25^oC to 40^oC. Additionally, a radiation output orientation module has been designed and integrated at the end of the optical fiber to meet various demands in phototherapy and photodynamic inactivation of bacterials.

Studying the drug use characteristics and commenting on the results of cerebral infarction treatment at Nghe An General Friendship Hospital Stroke Center in 2023

Dang Thi Soa, Nguyen Thu Hang, Vu Thi Thuy — Fri, 08 Mar 2024 11:10:49 +0700

With the desire to fully understand the use of drugs in the treatment of ischemic stroke to improve treatment effectiveness as well as safety for patients, the article presents the results of research on drug use characteristics and comments on the results of cerebral infarction treatment at the Stroke Center of Nghe An General Hospital. 113 medical records of infarction patients treated at the Stroke Center of Nghe An General Hospital from January 1, 2023 to June 30, 2023 were researched and analyzed. The results showed that thrombolytic therapy was consistent with the guidelines, most patients were stable and discharged from the hospital, and 6 adverse events were recorded, including 4 bleeding, 1 increased intracranial pressure, and 1 seizure.