Hong Duc University Journal of Science

CRITICAL PARAMETERS OF PEROVSKTE COMPOSITION Pr5/8Ca3/8Mn0.9875Pd0.0125O3, EXHIBITING THE CROSSOVER OF FIRST AND SECOND ORDER PHASE TRANSITION

2024-04-23T09:38:57+07:00

A compound of Pr_5/8Ca_3/8Mn_0.9875Pd_0.0125O₃ with orthorhombic structure was fabricated using a sol-gel method. The critical parameters with b=0.188(5) and g=1.005(3) calculated from the magnetic data around Curie temperature of 260 K are quite close to those of the tricritical mean field model. This indicates that the magnetic interaction in the compound is a combination of the long- and short-range interactions. It means the paramagnetic-ferromagnetic phase transition of Pr_5/8Ca_3/8Mn_7.9/8Pd_0.1/8O₃ compound is crossover of the first- and second-order phase transitions.

CALCULATION OF INTERFACE ROUGHNESS SCATTERING- LIMITED ELECTRON MOBILITIES AT LOW TEMPERATURES IN GaAs AND InAs QUANTUM WELLS

2024-04-23T09:38:58+07:00

In this paper, we present a study of the effects of interface roughness scattering-limited electron mobilities in GaAlAs/GaAs/GaAlAs and InGaSb/InAs/InGaSb quantum wells. We propose that interface roughness-related scatterings are generally key scattering mechanisms at low temperatures in heterostructures, especially thin quantum wells. Roughness is also shown to produce misfit deformation potential and misfit piezoelectric field as scattering sources in strained heterostructures. The analysis of our results clearly indicates that the significance of interface roughness scattering and, in particular, the influence of interface roughness correlation length and height is considerable. A comparison of our calculated results with published experimental data is shown to be in good agreement.

SYNTHESIS, STRUCTURAL CHARACTERIZATION, BIOLOGICAL ACTIVITY OF COMPLEXES OF Ni(II) WITH 5-BROMO-6-HYDROXYL-3-SULFOQUINOL-7-YLOXYACETIC ACID

2024-04-23T09:38:59+07:00

In this research, a derivative of quinoline, namely 5-bromo-6-hydroxyl-3-sulfoquinol-7-yloxyacetic acid as well as one complex of Ni(II) with this ligand [Ni(QBr-2H).H₂O].3H₂O (NiQBr) was synthesized. The molecular formulas and structures of the complex were determined using a combination of IR, EDX, ESI MS, ¹H NMR spectra and thermal analysis. In this complex, Ni(II) coordinated with QBr ligand through the oxygen atom of OH phenol, oxygen atom of OCH₂ groups and the oxygen atom of carboxylate groups. The results of antimicrobial resistance testing of complex showed that NiQBr complex exhibited high activities on Bacillus subtilis and Lactobacillus fermentum with low IC₅₀ from 0.61 - 0.71 μg/ml and NiQBr complex exhibited activities on Candida albican and Staphylococcus aureus with IC₅₀ from 26.30 - 104.30 μg/ml.

STRUCTURAL, FERROELECTRIC AND PIEZOELECTRIC PROPERTIES OF PbTiO3-MODIFIED COMPLEX 0.6Ba(Ti0.8Zr0.2)O3-0.4(Ba0.7Ca0.3)TiO3 CERAMICS

2024-04-23T09:39:00+07:00

In this paper, the structural and ferroelectric properties of PbTiO₃-modified 0.6Ba(Ti_0.8Zr_0.2)O₃-0.4(Ba_0.7Ca_0.3)TiO₃ ceramics are reported. The nonlinear electric polarization is observed at room temperature in 0.6Ba(Ti_0.8Zr_0.2)O₃-0.4(Ba_0.7Ca_0.3)TiO₃ and remained after the introduction of PbTiO₃. With increasing the PbTiO₃ concentration to 7 mol.%, high electrical remanent polarization of 13.11 µC/cm² is achieved. The large strain and S_max/E_max values were also obtained in PbTiO₃-modified compounds, where the highest piezoelectric coefficient values were estimated at around 642 pm/V for 3 mol.% PbTiO₃-addition into 0.6Ba(Ti_0.8Zr_0.2)O₃-0.4(Ba_0.7Ca_0.3)TiO₃ compounds. We expected that the ceramics prepared in our study might be a suitable candidate for applications in electronic devices.

A STUDY ON THEORETICAL PREDICTION OF NANOPOROUS STRUCTURES FROM ZnS SEMICONDUCTION MATERIALS

2024-04-23T09:39:03+07:00

Nanoporous structures have different properties and applications without changing the chemical composition. Therefore, predicting and synthesizing new nanoporous polymorphs of ZnS has a practical significance and has become one of the strong research directions. In this article, we perform a study based on the DFTB+ method to theoretically predict a series of new nanoporous structures of ZnS. These structures are created from the basic building blocks (ZnS)k (k = 9, 12, 16), they are clusters of molecules with high symmetry. Our results also indicate that all the nanoporous structures are predicted to be completely different mechanical and electrical properties. That proves it is possible to control the mechanical and electrical properties of materials through the configuration of the structure. The characteristic parameters of the ZnS nanoporous structures are examined in detail

AN INTRODUCTION TO THE HISTORY AND CULTURE OF THE DAO PEOPLE IN THANH HOA PROVINCE

2024-04-23T09:39:04+07:00

Dao people in Vietnam were known as a migrating community from China. Due to historical and social changes within the nation under the Qing dynasty, a part of the population had fled abroad including the Yao (in Chinese language); they crossed the mountains and established their villages in the highlands of Vietnam. There are 2 groups of the Dao in Thanh Hoa respectively Dao Quan Chet (meaning Dao with tight trousers) and Dao Do - Red Dao (meaning Dao with red color clothes). The aim of the article is to add more details of the history and typical ethnic cultural features of the Dao in Thanh Hoa province to enrich the knowledge of the Dao in Vietnam. In fact, the Dao people has a very rich and diverse cultural life. Although the Dao population is quite small in comparison to the other ethnic minority groups in Thanh Hoa, they have still reserved their unique cultural values which contribute to the richness and diversity of ethnic cultural characters in Thanh Hoa.

A STUDY ON SYNTHESIS, NMR SPECTRA OF SOME AZOMETHINE COMPOUNDS CONTAINING QUINOLINE AND FUROXAN SYNTHESIZED FROM EUGENOL IN OCIMUM SANCTUM L. OIL

2024-04-23T09:39:05+07:00

5,6-Dimethoxy-8-(3-methylfuroxan-4-yl)-2-methylquinoline (2) has been synthesized from eugenol, the main constituent of Ocimum sanctum L. oil, following the Döebner – Miler method in toluene – HCl heterogeneous system. The key 5,6-Dimethoxy- 8-(3-methylfuroxan-4-yl) quinoline-2-carbaldehyde (3) obtained by oxidation of compound 2 by SeO2 in dioxane solvent at 70 oC. Compound 3 was used as a key compound for further synthesis to 2 azomethines contain quinoline and furoxan moiety. The structure of the synthesized compounds was characterized by spectroscopic methods.

MORPHOLOGICAL AND ANATOMICAL CHARACTERISTICS, AND BIOACTIVE COMPOUND CONTENTS OF STEMONA TUBEROSA LOUR. COLLECTED IN VIETNAM

2024-04-23T09:39:05+07:00

Stemona tuberosa Lour. is one of the traditional medicines used for the treatment of cough, tuberculosis, antiseptics and external skin diseases. In Vietnam, Stemona tuberosa Lour is widely distributed from lowland to mountainous regions up to 1000 m altitude. To contribute to the database for study and use of this species, the information on morphology, anatomy, and bioactive compound content of alkaloids and tuberostemonines of 15 different provenances of Stemona tuberosa Lour. collected in different ecological regions of Vietnam is provided.

THE EXILE STATUS OF THE VIETNAMESE IN SOME CONTEMPORARY PROSE WORKS

2024-04-23T09:39:07+07:00

n the last decades of the twentieth century, when the post-war life became extremely poor and backward, many Vietnamese thought of finding a "promised land" in Europe. Many others, for personal reasons such as going to school, following family reunification, changing the current living environment, etc., have also left the country. The truth was only uncovered when, at the beginning of the twenty-first century, many prose works of writers who had experienced life in Europe were published. Thereby, readers can imagine the hardships, suffering, feelings of loneliness, lack of friendship, and lack of homeland of those who have left the country and lived in foreign lands. In this article, we focus on analyzing and explaining the exile status and life of Vietnamese immigrants and expatriates expressed in contemporary prose, while conveying a message of warning to decisions to leave hastily, delusionally; and to elucidate new features of the human image in Vietnamese literature.

SYNTHESIS OF SOME o-AMINOPHENOL DERIVATIVES AND ANTIOXIDANT ACTIVITIES

2024-04-23T09:39:08+07:00

o-Amino phenol derivatives are well-known reagents in organic synthesis. Two o-aminophenol 6a, 6b were synthesized successfully from corresponding o-nitrophenol derivatives in 75% over the yield in 5 steps. Two steps were promoted with microwave irradiation for 4-6 minutes in high yield. Conversion of nitro to amino group was reduced with Na₂S₂O₄ in ethanol in 75% yield. Structures of them were elucidated carefully by IR and NMR methods. Two compounds 6a, 6b were exhibited antioxidant activity with SC₅₀= 12.23 mg/mL and 22.96 mg/mL.

ENHANCING CRITICAL THINKING COMPETENCE FOR HIGH SCHOOL STUDENTS THROUGH TEACHING HAIKU POETRY

2024-04-23T09:39:08+07:00

Critical thinking is one of the most important competencies of high-quality human resources. Enhancing this competency must be the vital objective of Vietnam's education. However, in reality, the critical thinking competence of high school students is still low, and the development of this capacity for them has not been paid attention to in teaching Literature. Haiku poetry, which is a traditional genre of Japanese poetry, has great potential in developing critical thinking competence thanks to its characteristics. Thus, it is appropriate, and necessary to associate teaching Haiku poetry with enhancing critical thinking for students. In this article, we propose several measures to enhance critical thinking competence for students through teaching Haiku poetry.

STABILIZATION OF TWO-DIMENSIONAL SINGULAR ROESSER SYSTEMS

2024-04-23T09:39:09+07:00

This paper is concerned with the stabilization problem via state-feedback control for a class of two-dimensional (2-D) singular Roesser systems. Based on a 2-D Lyapunov function scheme, and by utilizing zero-type free matrix equations, sufficient conditions in the form of linear matrix inequalities (LMIs) are first derived to guarantee the admissibility (causality and asymptotic stability) of the closed-loop systems. Then, a stabilizing state-feedback controller (SFC) can be implemented using tractable LMIs conditions.

CHANGES IN MARRIAGE OF THE MUONG PEOPLE IN THANH HOA

2024-04-23T09:39:10+07:00

Marriage is a common custom of all ethnic groups in Vietnam as well as in the world. For the Muong families, marriage is especially important. In traditional society of the Muong, the wedding took place for long days with many different rituals. Nowadays, under the influence of the market economy and international integration, the practices of culture and marriage rituals of the Muong people have been undergoing significant changes. Specifically, changes in personal thoughts, in criteria for choosing a partner, in marriage rituals and practices, offerings, transformation in costume, in eating, and celebrating weddings. The changes have profoundly affected the traditional wedding culture of the Muong, thereby shaping a vivid and complex picture of cultural life of the Muong nowadays.

ISOLATED COMPOUNDS FROM AERIAL PARTS OF ABELMOSCHUS SAGITTIFOLIUS

2024-04-23T09:39:10+07:00

Abelmoschus sagittifolius is a species belonging to the Malvaceae family. According to traditional medicine, the root tuber of Abelmoschus sagittifolius was used to treat diseases such as cough, constipation, neurasthenia, malnutrition, boils, back pain, and stomach pain. In this study, from Abelmoschus sagittifolius aerial parts collected in Vinh Hung commune, Vinh Loc district, Thanh Hoa province, three compounds were isolated including sitostenone (1), tiliroside (2) and kaempferin (3). The structures of these compounds were identified by NMR, MS spectroscopic data and comparison with the reported literatures.

PROMOTING STUDENTS’ SELF-REGULATED LEARNING USING A SELF-RECORDED VIDEO TASK IN A COURSE ON PRESENTATION SKILLS

2024-04-23T09:39:11+07:00

Given the importance of self-regulation in boosting students' self-efficacy and achievements, this study examined the impact of the self-recorded video task on promoting students' self-regulated learning. The study participants were 39 English majors at Hong Duc University who attended a course on presentation skills. Data were collected from the student's scores for the task and a questionnaire. Findings show that the self-recorded video task promotes students' self-regulated learning. In addition, each phase of self-regulation was not linear in a time-ordered sequence. Instead, goal-setting, monitoring, evaluating processes, re-setting goals, and performing task strategies were all intertwined.

MATHEMATICAL MODEL OF FILTERED INSULATION FOR HIGH-TEMPERATURE INSTALLATION

2024-04-23T09:39:12+07:00

A large amount of heat in the combustion of fuel in a high-temperature furnace is lost through the external fencing and heats up the smoke. Hence, reducing heat loss through the external fencing is necessary to save fuel, natural resources. This study provides the results of a mathematical model of heat transfer on a special surface relief in the air channels of the external walls of a high-temperature installation containing heat transfer intensifiers to improve fuel combustion efficiency.

PERIODIC SOLUTION TO NONDENSELY DEFINED DIFFERENTIAL EQUATIONS WITH INFINITE DELAY

2024-04-23T09:39:12+07:00

In this paper, we investigate the existence and uniqueness of periodic solution to a class of nondensely defined differential equations with infinite delay of the form

FORMS OF TERRITORIAL ORGANIZATION OF THE MANUFACTURING INDUSTRY IN THANH HOA PROVINCE

2024-04-23T09:39:13+07:00

The territorial organization of the manufacturing industry in Thanh Hoa has been contributing to promoting the development and transforming the economic structure of the province towards modernity. However, the problem of developing the organizational forms of the manufacturing industry here is still inadequate. This study analyzes the above issue from the perspective of economic geography, and at the same time makes comments and recommendations to serve as a basis for planning and developing forms of territorial organization of the manufacturing industry in Thanh Hoa province.

CALCULATING THE CARBON FOOTPRINT OF SHRIMP FARMING IN VIETNAM: THE CASE STUDY IN PHU VANG DISTRICT, THUA THIEN HUE PROVINCE

2024-04-23T09:39:13+07:00

Shrimp farming is one of the most rapidly growing aquaculture, which globally has been associated with considerable revenue for farmers. In Vietnam, shrimp aquaculture is now one of the most important aquaculture practices in terms of area, production, employment and foreign exchange generation. However, they were also guilty of polluting the environment with greenhouse gas emissions. This study represents an attempt to estimate the carbon footprints of shrimp farming systems based on farm data. Phu Vang District of Thua Thien Hue Province was selected as a case study. The primary data was obtained from fieldwork and interviews with the different actors involved in the selection of shrimp production. The strength of the approach does not lie in producing exact carbon footprints, but in providing a range in which the footprints could fall. Overall, the results of this study demonstrate that the annual carbon footprint of shrimp farming in Hue province is 0.0021 tCO2e or 2.1 Kg CO2e/Kg of shrimp weight. In which, feed consumption contributes most to total greenhouse gas emissions of shrimp farming activities; while energy use such as electricity, diesel oil and human labor also play important roles. The results also indicate the significant differences among farming types in terms of farming productivity and carbon footprint contribution. The on-sand farming system produced the highest yield of shrimp per hectare, however, it has about twice as much greenhouse gas emission per kg shrimp than those grown in high-tide and low-tide farming systems. More sustainable farming practices should be implemented to reduce the carbon footprint or amount of greenhouse gas emissions from shrimp farming activities.