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This work focuses on a dynamic electrical circuit whose dynamics are affine in the control input. Such dynamics are considered to be re-expressed in a canonical form, namely the port-Hamiltonian (pH) representation with dissipation, where the Hamiltonian is a quadratic function and has the unit of energy or power. On this basis, it allows revealing the transformation of energy (or power) inside the system, including the energy supply, storage and dissipation, thereby facilitating Lyapunov-based or energy-related control approaches for stabilization and optimization purposes. Two pH representations are proposed and compared; the first one is established with difficult-to-measure states while the second one is obtained with easier-to-measure states.

Sử dụng năng lượng mặt trời trong nuôi trồng thủy sản là giải pháp phát triển bền vững mà nhà nước đang khuyến khích. Bài báo này nhằm mục tiêu giới thiệu và cung cấp phương pháp triển khai giải thuật dò tìm và bám theo điểm công suất cực đại của tấm pin quang điện (tấm pin năng lượng mặt trời) dựa trên độ điện dẫn của tấm pin (giải thuật Incremental Conductance Maximum Power Point Tracking – Ind. Cond. MPPT). Đây là phần quan trọng để tạo cơ sở triển khai sử dụng năng lượng mặt trời trong các ao nuôi, đặc biệt là giải quyết nhu cầu về năng lượng cho các dàn quạt nước ao tôm (dùng cho cung cấp ôxy và đảo nước trong ao), vì nó giúp khai thác tối đa nguồn năng lượng từ tấm pin năng lượng mặt trời. Dựa trên cơ sở lý thuyết về mô hình của tấm pin quang điện, giải thuật Incremental Conductance được triển khai trong cấu hình mạch chuyển đổi điện áp DC-DC kiểu boost xen kẽ được điều khiển bởi bộ điều khiển kỹ thuật số khả trình (vi điều khiển STM32F1). Kết quả triển khai cho thấy điện áp tại điểm công suất cực đại của hệ pin được duy trì ổn định, công suất trích xuất được điều khiển bám theo công suất khả dụng tối đa của hệ các tấm pin, hệ thống với giải thuật Ind...

During the thirty-year resistance (1945-1975), the policy of the Democratic Republic of Vietnam was simultaneously building the country while maintaining the resistance war in order to self-strengthen the country for the final victory. Therefore, during the nine-year resistance war against the French colonialism, the Party and Government-led by President Ho Chi Minh-paid close attention on developing a national and a democratic education, a popular and scientific culture. The Party’s guidelines and policies were relatively comprehensive and suitable with the circumstance of Vietnam as well as the human development tendencies at that time. [ABSTRACT FROM AUTHOR]

During the American War, the Truong Son trail has become a legendary trail, a "labyrinthine battle in forest". Haft a century since its formation and 34 years since the end of the war, Truong Son Trail had been a research subject for both politicians, military commanders and historians who agreed that: the United States failed in the Vietnam War for its inability of destroying this trail. The Truong Son trail was not simply a road but, above all, it was the symbol of Vietnamese nation's desire for independence, freedom and national unification. This article focuses on discussing the foundation, development, and significant role of the Truong Son trail. Based on these analyses, the article highlights the military arts deployed by the Vietnamese armies in the western frontier during the American war. [ABSTRACT FROM AUTHOR]

Three compounds were isolated from the methanol extract of the species Enhalus acoroides using a combination of several chromatographic methods. The structural elucidations of those compounds were analysed using ESI-MS and NMR. Compared with published data, the results showed that methyl pheophorbide a, adenosine, and uracil were three compounds.

The composition of fish species in the Ngan Pho River basin, Huong Son district, Ha Tinh province, was studied from 2020 to 2022. The study aims to evaluate the diversity of fish species and their situation of exploitation in the area. Our results have found 78 species of fish distributed in 8 sampling points in the basin. Forty-eight fish species have been identified as high economic value, of which 16 species were found to be cultivated. Combined with the results of previous research, we have determined 107 fish species belonging to 72 genera of 20 subfamilies and 29 families belonging to 11 orders in the Ngan Pho River basin. Moreover, 39 species were discovered for the first time distributed here. In addition, some species were not reencountered during the field survey, including marine species migrating for food, such as Echidna polyzona, Ophichthus microcephalus, and Pisodonophis boro. They are possibly impacted by anthropogenic factors such as sand exploitation along the basin and changes in the flow from the Lam River estuary to the La River tributary and then to the Ngan Pho River.

This study utilized a Structural Equation Modeling approach to model and measure the influence of environmental attitudes and preschool teachers' beliefs regarding environmental education. Data was collected from 324 preschool teachers in Hanoi, Danang, and Ho Chi Minh City through an online questionnaire. SmartPLS software was used for data analysis. The results indicated that the environmental attitudes of preschool teachers have a significant, positive, and strong influence on their beliefs regarding environmental education, with path coefficients valued at 0.734 (p < 0.05), the model's explanatory power of 0.539, and the effect size of 1.170. In addition, this study provided reliability and validity scales for environmental attitudes and preschool teachers' beliefs regarding environmental education. These findings imply that it is necessary to cultivate and enhance a positive attitude toward the environment among preschool teachers through initial preschool teacher training and professional development for in-service preschool teachers. This will help solidify their beliefs about environmental education.

Bài toán tái nhận dạng người hướng tới việc tự động theo vết và tìm kiếm lại đối tượng di chuyển trong hệ thống camera giám sát với góc nhìn của các camera không chồng lấp nhau. Khi một đối tượng được phát hiện trong khung ảnh, các đặc trưng về hình dáng bên ngoài của đối tượng sẽ được trích xuất thông qua việc xây dựng các mô hình đặc tả. Tuy nhiên, phần hình nền còn lại của khung ảnh trích xuất đối tượng thu được từ giải thuật phát hiện người vẫn có thể ảnh hưởng đến mô hình tái nhận dạng người. Vì vậy, trong bài báo này, chúng tôi đề xuất chuỗi xử lý bài toán tái nhận dạng người với hai nhiệm vụ chính: loại bỏ vùng nền trong khung ảnh đối tượng đã được phát hiện và củng cố đặc trưng tách từ các mảnh ghép cục bộ dùng để phân biệt hai đối tượng khác nhau. Việc kết hợp này nhằm nâng cao mức độ tin cậy của việc truy vấn cùng một đối tượng ở hai camera khác nhau với góc nhìn không chồng lấp.

Motors play a crucial role in production systems. However, not everything always goes smoothly, and motor failures are one of the common challenges in the production process. Misalignment of the drive shaft is a frequent motor fault caused by improper installation or damage to machine components. This study proposes the design of a monitoring and fault diagnosis model for DC motors, which includes: (i) a PID controller for motor speed control; (ii) a vibration signal acquisition unit; and (iii) a motor monitoring unit via Blynk and signal processing for fault diagnosis. In the model, motor faults are classified using a convolutional neural network (CNN) based on analog signals that have been transformed to the frequency domain and denoised. Experimental results demonstrate that classification using the convolutional neural network is highly accurate and stable.

The use of fiber-reinforced polymer (FRP) strips as an external strengthening method has gained widespread acceptance for enhancing the capacity of aging reinforced concrete (RC) beams. Despite extensive research and practical applications, there exist unresolved issues necessitating further investigation, including interface bonding, failure mechanisms, and the development of accurate predictive models for shear strength, considering diverse parameters. This paper systematically reviews shear strength formulas applied in the strengthening of RC beams using FRP strips. An extensive experimental dataset is compiled from diverse sources to support the analysis. Utilizing this dataset, a novel ensemble learning model is developed for predicting the shear strength contributed by FRP strips. Following the training of this model, the important score of each input parameter is also assessed. The findings presented herein contribute to a deeper understanding of the strengthening effectiveness of FRP strips on RC beams.

Despite its importance and urgency, the problem of hospitality food waste (FW) has not received much attention from academics. This paper has contributed to the field of FW by examining the FW practices employed by luxury hotels in Vietnam. 25 semi-structured interviews have been conducted with employees working in hotels in Danang and Quangnam. A qualitative thematic coding analysis was employed to identify themes. The results show that buffet leftovers were the most wasteful type, compared to preparation and plate waste. The study indicates that the prioritization of surplus food reuse and redistribution, particularly the sale of FW for animal feed, takes precedence over prevention practices. Customers were found to create more challenges than hotel employees regarding barriers to more effectively managing the FW issue. The study provides practical implications for policymakers to formulate and implement strategies aimed at enhancing the effectiveness and sustainability of FW management practices.

The Steiner tree problem in graphs (SPG) is one of the most studied problems in combinatorial optimization because of its theories and applications. It is one of the foundations to develop a Wireless Sensor Network (WSNs), such as multicast and topology design. SPG is an NP-Hard problem, and many heuristic and approximation algorithms have been proposed. Thus, this study proposes a Hybrid Genetic algorithm (HGA) to solve SPG. This study is the binary string representation for a set of chosen edges. To increase the diversity of the population and avoid falling into local optimization, we use a 2-longest Distance strategy, dynamic crossover rate, and chosen solutions must differ by at least 5%. The experiment results show that the HGA algorithm's running time equals 153.83% of the GA algorithm's, the deviation found by HGA, and the optimal distance only equals 65% that of GA.

We used the genetic algorithm and quantum chemical calculations to study the structures of the Sc2B6 cluster. The global minimum energy structure has the shape of a hexagonal bipyramid with an Sc atom at each apex and a B6 ring that belongs to the D6h point group symmetry. The second most stable structure has the Cs point group symmetry and can be formed by substituting a Sc atom for a B atom in the ring and a B atom for Sc in one of the apexes. From the computational results, the Sc2B6 cluster is found to be a good candidate to form a nanomaterial for treating CO gas.

Food classification has always piqued the interest of both domestic and international researchers, but numerous challenges remain. We present the dataset UIT-TASTET21, which contains over 77,000 color images of 18 traditional Vietnamese Lunar New Year dishes. We have experimented with classification using feature vectors from network architectures such as VGG16, Inception-v3, ResNet-50, Xception, and MobileNet-v2 to train support vector machines (SVMs), meeting the dataset’s challenges and laying the groundwork for the development of many optimal methods in the future that promise scientific breakthroughs in the service and commercial industries. At the same time, the authors desire to share a piece of Vietnamese cuisine’s distinctiveness with worldwide friends.

Artificial intelligence (AI) has found applications across various sectors and industries, offering numerous advantages to human beings. One prominent area where AI has made significant contributions is in machine learning models. These models have revolutionized various fields, benefiting society in numerous ways, from self-driving cars and intelligent chatbots to automated facial authentication systems. However, in recent years, machine learning models have been the target of various attack methods. One common and dangerous attack method is adversarial attack, where modified input images can cause misclassification or erroneous predictions by the models. To confront that challenge, we present a novel approach called adversarial retraining that uses adversarial examples to train machine learning and deep learning models. This technique aims to enhance the robustness and performance of these models by subjecting them to adversarial scenarios during the training process. In this paper, we survey detection methods and propose a method to detect adversarial examples using YOLOv7, a commonly used intensive research model. By training adversarial retraining and conducting experiments, we show that the proposed method is an effective solution for helping deep learning models detect certain cases of adversarial examples.

Tình trạng các tân SV (SV) của các trường đại học ở Việt Nam nói chung và tại trường Đại học Cần Thơ (ĐHCT) nói riêng thường phải đối mặt với rất nhiều khó khăn trong cuộc sống, đặt biệt là trong học tập, luôn là mối bận tâm của nhà trường, giảng viên (GV) và gia đình. Mục tiêu của nghiên cứu ?Thuận lợi và khó khăn trong học tập của SV năm nhất ĐHCT? là khảo sát những cơ hội và thách thức trong học tập của các SV năm nhất tại nhà trường, từ đó đưa những đề xuất mang tính khả thi để giúp các tân SV sớm khắc phục những khó khăn, nhanh chóng thích nghi với môi trường học tập ở bậc đại học và đạt kết quả học tập tốt nhất. Để đạt được mục đích đó, nhóm nghiên cứu đã sử dụng phương pháp khảo sát bằng phiếu điều tra và bảng câu hỏi phỏng vấn cho cả tân SV lẫn giảng viên, cố vấn học tập (CVHT) tại nhà trường. Báo này trình bày kết quả nghiên cứu định lượng từ thông tin do 703 SV năm nhất tại trường cung cấp thông qua phiếu điều tra. Kết quả nghiên cứu cho thấy rằng bên cạnh một số thuận lợi nhất định, các SV năm nhất gặp rất nhiều yếu tố khó khăn ảnh hưởng đến chất lượng học tập của SV. Những khó khăn này phát sinh từ ba nhóm yếu tố chính là (1) bản thân tân SV, (2) cán bộ giảng dạy và CVHT và (3) nhà trường, gia đình và bạn bè. Trong đó, hai nhóm yếu tố đầu tiên là gây ra nhiều trở ngại nhất cho hoạt động học tập của SV năm nhất. Dựa vào kết quả khảo sát, chúng tôi cũng tổng hợp được những đề xuất nhằm giúp các tân SV có thể vượt qua những khó khăn trong học tập.

TMD devices are considered a reasonable solution to enhance the bearing capacity of the structures under unpredictable impacts from external forces because their operating principle is quite simple and does not vary the main structure. This paper investigated the influence of the TMD device, including its mass and stiffness, on the vibration reduction of the primary structure, a basic steel beam. In which, a small-scale steel beam model with boundary conditions through experiments was carried out. Then, simulated the experiment using MATLAB based on the experimental results to study the effect of TMD on the vibration of the structure. The results exhibit that the vibration-damping capacity of the main structure increases as the TMD mass increases. The stiffness of the main structure is less than 1,8k for both TMD 3% and 5%, resulting in the rapid increase of oscillation reduction efficiency.

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 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%.

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.

Ma Van Khang is a prominent novelist who has made significant contributions by delving into the subject of intellectuals. The author often contemplates the role of intellectuals in the society. There have been numerous research works on this central theme in Ma Van Khang's novels, and they have provided valuable assessments. However, interpreting Ma Van Khang's artistic choices and the depth of his perspective on the issues he addresses continue to provoke discussions. By situating Ma Van Khang's novels within the broader context of the fluctuating currents of modern Vietnamese fiction that focus on intellectuals and by examining the author's consciousness of the dynamic relationship between literature and life, this article contributes to explaining why the issues raised in the writer's works and the way he presents them have garnered positive responses from readers.

In this research paper, an adaptive sliding controller designed to enhance seismic response mitigation in structural systems with prescribed performance is presented. The performance function converts the error to a converging error within a predefined neighborhood. Furthermore, the adaptive algorithm is also designed to ensure the controller operates effectively under uncertain system parameters. The serial–parallel estimation model was adopted for parameter vector and error model. The Lyapunov function is chosen to ensure the convergence stability of the control strategy. Through comprehensive theoretical analysis and simulation studies, the efficiency of the performance function has been simulated for a one-degree-of-freedom structure. Simulation results demonstrated the effectiveness of the control algorithm in reducing the seismic response.

This study aims to recycle the coal bottom ash (CBA) for making environmentally friendly construction bricks. In the brick proportion, CBA was employed as fine aggregate to replace 0, 30, 50, 70, 85, and 100% of stone powder. The results demonstrate that, the compressive strength, ultrasonic pulse velocity, electrical resistance, and thermal conductivity of the 28-day bricks were in the ranges of 16.1 ÷ 61.3 MPa, 3469 ÷ 4208 m/s, 20.2 ÷ 54.6 kΩ.cm, and 0.75 ÷ 2.2 W/mK, respectively. According to scanning electron microscopy analysis, the rise in CBA content was associated with an increase in the number of voids and pores of bricks, which led to a less dense microstructure and a negative impact on the brick’s quality. However, all specimens created for this investigation met the standards of the official Vietnamese standard and were categorized as grade M15.0 or higher according to their qualities.

This paper analysis the magnetic features including flux linkage and air-gap flux density in interior permanent magnet synchronous motor (IPMSM) with delta-shaped PM used for electric vehicles (EVs). Research motor models are based on the motor of Nissan Leaf called EM61 taken from experiment reports, and the analysis is based on finite element analysis (FEA). The analysis is performed by adjusting the existence of permanent magnets (PMs) and flux barriers (FBs) as well as the amplitude and phase angle of excitation current which affect the torque production, phase flux linkage, and air-gap flux density under two temperature conditions. Through this analysis, the influence of each object, its position (i.e., the inner and outer layer of PM and FB), and PM-FB interaction on the magnetic features of IPMSM are expressed. The role of these PM-FBs on magnetic features also helps to point out some indications for engineers when designing an IPMSM.

The aim of this study is to assess how different extraction temperatures affect the in vitro antioxidant potential of polysaccharides derived from the leaves of Myxopyrum smilacifolium. The findings indicated that, the polysaccharides exhibit the highest antioxidant activity when extracted at a temperature of 90°C. Fourier transform infrared spectroscopy analysis confirmed the presence of characteristic absorption groups typically found in polysaccharide structures in the PS-T90 sample. The average molecular weight of the extracted polysaccharides was approximately 9.30×105 Da. The total antioxidant capacity of PS-T90 was determined to be 0.2646 ± 0.0007 mg GA/g or 0.1725 ± 0.0007 mg AS/g. Additionally, the IC50 values for the polysaccharides against 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radicals were measured to be 1.04 mg/mL and 3.37 mg/mL, respectively. These exceptional bioactive properties suggest the potential of PS-T90 as a valuable resource for antioxidant development.

Camellia piquetiana, one of the endemic species of Vietnam, is classified as Critically Endangered (CR) by the IUCN. A reassessment of its conservation status and research into propagation methods are essential for its conservation. Our survey recorded 246 mature individuals in the wild at three locations in Lam Dong Province: Bao Loc City, Bao Lam District, and Da Huoai District. The conservation assessment for this species, determined with GeoCat software, is still CR. Propagation by partially uncoated seeds had a higher propagation efficiency than by coated seeds. The germination percentage was 92.22%; the seeds began germination after 11 days and finished after 29.33 days. The results showed that stem cuttings immersed in a concentration of 500 ppm indole-3-butyric acid for 10 minutes with a 100% coir substrate gave the highest survival percentage (90.00%), rooting percentage (86.67%), average number of roots (4.54), root length (4.86 cm), and rooting index (21.98) after 90 days.

Năm hợp chất gồm hai dihydrochalcone, 2’,6’-dihydroxy-4’-methoxydihydrochalcone (1), dihydroflavokawin B (2), một flavanone, pinocembrin (3) và hai diarylheptanoid, dihydroyashabushiketol (4), 5-methoxy-1,7-diphenyl-3-heptanone (5) đã được phân lập lần đầu tiên từ cao chiết n-hexane của loài Conamomum rubidum. Cấu trúc hóa học của chúng được xác định bằng phương pháp phổ cộng hưởng từ hạt nhân và so sánh với các dữ kiện phổ đã công bố. Hoạt tính kháng viêm trên mô hình ức chế sản sinh NO và gây độc tế bào của các hợp chất đã được đánh giá. Theo đó, hợp chất 2, 4 và 5 ức chế sản sinh NO với các giá trị IC50 trong khoảng từ 58,16 ± 3,02 đến 81,95 ± 2,87 µM. Hợp chất 1 ức chế tế bào ung thư phổi SK-LU-1 với giá trị IC50 = 58,45 ± 2,26 µM.

This study investigates flowable dredged soil backfill using air-foam technology and simulates a bridge approach structure under high-speed train loads. A comparison between conventional cement-treated soil (CTB) and innovative flowable dredged soil backfill solutions reveals crucial findings: Resilient modulus tests highlight the significant impact of cement and air foam, favoring mixtures with over 210 kg/m3 cement content and less than 10% air-foam, resulting in a resilient modulus of 354 MPa. Finite Element Method (FEM) simulations show CTB compliance with k1/k2 standards for all track options and the effectiveness of lightweight soil, especially Silty Soil (SM), in preventing critical k1/k2 increases. The lightweight soil exhibits superior performance through FEM analysis, settling only 3 mm after 800,000 cyclic train loads compared to nearly 5 mm in conventional CTB systems. This confirms the feasibility of lightweight dredged soil backfill in strengthening weak bridge approach foundations, enhancing railway track infrastructure sustainability and performance.

This study investigates the performance of controlled low-strength material (CLSM) in the challenging Mekong Delta climate, which experiences rapid weather fluctuations, acid rain erosion, uneven mixture gradation, and subpar aggregate quality. Additionally, difficulties in sieving and quality control have led to the disposal of dredged soil in construction sites. The research aims to enhance the practical use of CLSM as a foundation for rural roads in the Mekong Delta by incorporating dredged soil and mineral additives (6% silica fume, 25% bottom ash) under various curing conditions, including normal, acidic, and salted environments. The study assesses CLSM strength through flowability, setting time, and unconfined compressive strength tests. Findings highlight the significant influence of curing conditions on both early and 28-day CLSM strength, with harsh environments compromising cement hydration. Optimizing dredged soil content and mineral components can bolster CLSM strength and promote sustainable use of dredged soil in construction.

Hiện nay, phương pháp von-ampe hòa tan anot xung vi phân (DP-ASV) sử dụng điện cực biến tính được cho là có độ chọn lọc, độ nhạy cao và giá thành rẻ. Trong nghiên cứu này, điện cực glassy carbon được biến tính bằng graphene oxide dạng khử kết hợp với màng bismuth in situ (BiFE/ErGO-GCE) để xác định đồng thời Cd(II) và Pb(II) trong môi trường nước. Một số thông số đã được nghiên cứu: lượng vật liệu graphene oxide, nồng độ của Bi(III) và thông số của phương pháp DP-ASV. Giới hạn phát hiện của Cd(II) và Pb(II) được xác định là 1,50 ppb và 1,39 ppb. Thêm vào đó, điện cực biến tính BiFE/ErGO-GCE cũng được áp dụng xác định đồng thời Cd(II) và Pb(II) trong hai mẫu nước sông Hương và An Cựu. Kết quả được so sánh với phương pháp khối phổ plasma cảm ứng cho kết quả có ý nghĩa.

Trong nghiên cứu này, vật liệu nghiên cứu là than bùn được hoạt hóa bằng H3PO4 ở nồng độ 2,0 M. Các mẫu sau khi tổng hợp được đặc trưng bởi một số phương pháp như EDX, XRD, SEM, BET và FTIR. Tính chất hấp phụ của vật liệu được đánh giá thông qua khả năng loại bỏ ion Cd2+ trong dung dịch nước. Đặc trưng vật liệu cho thấy mẫu than bùn sau khi hoạt hóa có diện tích bề mặt riêng và độ xốp cao hơn so với mẫu than bùn thô. Nghiên cứu cho thấy dữ liệu thực nghiệm hấp phụ ion Cd2+ trên than bùn được hoạt hóa được mô tả tốt đồng thời bởi cả hai mô hình đẳng nhiệt Langmuir và Freundlich, tuy nhiên mô hình đẳng nhiệt Langmuir tỏ ra phù hợp hơn. Vật liệu than bùn được hoạt hóa đạt dung lượng hấp phụ cực đại qm 29,07 mg/g. Ngoài ra nghiên cứu còn cho thấy sự hấp phụ ion Cd2+ trên than bùn hoạt hóa tuân theo mô hình động học biểu kiến bậc 2. Từ những kết quả nghiên cứu trên cho thấy vật liệu hấp phụ từ than bùn có nhiều tiềm năng trong việc loại bỏ các ion kim loại nặng trong dung dịch nước.

The purpose of research is to assess the seasonal changes of water quality in mainstream and in specific tributaries in the Ca River Basin. Water samples were collected in the dry season (May 2021) and in the beginning of the rainy season (September 2021) from 4 sites located on Ca River’s mainstream and 5 sites located on Ca River’s tributaries to analyze water quality parameters. Results indicated that physical parameters (pH, EC, salinity, DO) and and heavy metals (As, Cu) are within the standard values according to the National Technical Regulation on Surface Water Quality QCVN 08-MT:2015/BTNMT for domestic water supply purposes (Columne A1). The concentration of nutrients measured in the tributaries is higher than those in the mainstream due to the contribution of nutrients and organic materials from agricultural runoff. In addition, the water flow in the tributaries is lower than in the mainstream, as a result, the concentration of nutrients tends to be higher in the tributaries. The samples revealed that the concentration of nutrients (NO3-, TN, PO43-, TP) and chemical oxygen demand (COD) appeared higher in the beginning of the rainy season than in the dry season. The increase of nutrient concentrations can be explained by the leaching of nutrients into the river. In general, the water quality of Ca River’s tributaries during the rainy season have a high nutrient concentration and also the risk of eutrophication.

This study uses a mixed-methods approach to investigate the experiences of Vietnamese university students with disabilities (visual/mobility impairments) with e-learning as a consequence of emergency remote teaching during the COVID-19 pandemic. An analysis of the ideas of 20 surveyed students with disabilities at eight universities in Ho Chi Minh City and six students interviewed afterward shows that students can change their study habits to adapt to e-learning and to enjoy this model of learning. However, the participants revealed that they also want to experience face-to-face learning so that they can interact with their lecturers and peers more effectively and in more diverse ways, as well as assimilate lectures more easily. Furthermore, the research shows that various adjustments should be made by system designers, universities, and lecturers to make e-learning friendlier to disabled students. The recommended adjustments include designing easy-to-use learning tools and platforms, providing lecturers with the necessary tools and facilities to design lessons appropriate for all students, providing psychological and technical support for disabled students, choosing user-friendly learning applications and platforms, providing students with suitable learning resources, and modifying testing and assessment methods.

In this study, a total of 30 yeast isolates were recovered from local fruits in Thua Thien Hue province. Genetic characterization based on the ITS sequences identified isolates belonging to 3 species including Saccharomyces cerevisiae, Lachancea fermentati, and Clavispora fructus, with high sequence homology (over 99%) compared to published sequences in the GenBank. All identified S. cerevisiae isolates could grow well at 30°C and ferment several sugar including fructose, galactose, sucrose, mannose, maltose, and raffinose with different performances, but were inhibited at temperature higher than 35°C. The strains also grew well in the medium containing 5% ethanol (v/v) and 200 g/L glucose, but their growth ability was decreased gradually with an increase in ethanol and glucose concentrations. Interestingly, D14 strain was able to grow in the medium supplemented with 12% of ethanol, and 500 g/L of glucose at 45°C, while D7 strain could utilize both mannitol and glycerol at a low level. Our results also indicated that some strains have relatively high sedimentation efficiency, which are favorable conditions for beer fermentation and biomass recovery. The isolated yeast strains with good tolerance properties may provide a potential source of valuable raw materials for applications in beverage production and food processing.

The hierarchical nanostructures (3D) with their large specific surface area and abundant pores usually possess unique physical and chemical properties for various important applications. In this report, we have introduced simple and scalable routes to successfully synthesize 3D iron oxide nanostructures, including porous cubes and bird nest-like architecture. The 3D sponge-like Fe2O3 nanocubes were formed by an annealing process of perfect Prussian Blue (PB) microcubes, which were built from small nanoparticles linked together. Whereas, the 3D bird nest-like Fe2O3 nanostructures were formed by the transformation of C@FeOOH nanoflower precursors, which were constructed by primary nanorods. The results indicated that the obtained materials show monodispersity, uniform morphology, ultra-porosity and extremely high specific surface area. With unique characteristics, the 3D Fe2O3 nanostructures could be potential candidates for various important fields such as catalysts, absorption and gas sensors.

As a traditional medicinal plant in Vietnam, Myxopyrum smilacifolium has been used for a long history to treat cough, nervous disorders, numbness, rheumatism, and cephalalgia. Nevertheless, reports on the antioxidant activity and extraction of M. smilacifolium polysaccharides are still very rare. This study was designed to extract a high yield of polysaccharides from the M. smilacifolium trunk and characterize it. As a result, the maximum yield of the polysaccharides of 5.13 ± 0.05% was obtained with an extraction time of three hours, extraction temperature of 100 oC, the ratio of water to sample of 1:50 as extraction solution, extraction number of times 3, and the ratio of ethanol to extract volume 5:1 (v/v). Polysaccharides was characterized by Fourier transform infrared spectroscopy (FT-IR) and high-performance gel-permeation chromatography (HPGPC). The average molecular weight of extracted polysaccharides was around 3.78 × 105 Da. In vitro assays dan impressive antioxidant activities of the extracted polysaccharides, containing 0.2423 ± 0.0028 mg GA/g or 0.2142 ± 0.0007 μmol AS/g. The IC50 values of polysaccharides in the DPPH and ABTS methods were 0.89 mg/mL and 3.85 mg/mL, respectively. These findings exhibited the potential for application or further research and development of polysaccharides from Myxopyrum smilacifolium.

This study uses the Environmental Impact Quotient (EIQ) to assess the health and ecological risks caused by fungicides used in chrysanthemum cultivation upstream of Xuan Huong Lake, Da Lat city. Survey results reveal that 134 farmers use 21 fungicides with 18 active ingredients on a total area of 35.2 hectares. In all, 18 fungicides with an EIQ at the level of “unlikely to be hazardous” (EIQ < 25) are used on about 95% of the acreage, and 3 fungicides with an EIQ of “slightly hazardous” (25 < EIQ < 50) are used on the rest of the area. The Field Use EIQ of fungicide was rated very low in only 8.2% of the survey area and moderate in 48%. Areas with high and very high ratings account for 3% and 41%, respectively. Using fungicides according to the instructions can reduce the Field Use EIQ values in cultivated areas by 38% and return areas with high and moderate ratings to a low rating. Therefore, it is necessary to instruct farmers on the safe use of fungicides and to recommend those with low EIQ values for chrysanthemum cultivation.

The teaching staff has a very important position and role, is a factor that plays a decisive role in the quality of teaching National Defense and Security Education at universities. However, the quality of the teaching staff in charge of National Defense and Security Dducation, besides the advantages, still exists some certain limitations. Through analyzing and explaining theoretical and practical issues about the quality of the teaching staff, some key solutions have been proposed to improve the quality of these lecturers, meeting the current requirements of education and training innovation.

The study was conducted from June to December 2021 to assess the technical – financial aspect and the existing advantages and difficulties of the giant freshwater prawn culture in coconut garden ditch culture by interviewing 32 farming households in Thanh Phu district, Ben Tre Province. The study results showed that the average area for each ditch was 0.38 ± 0.29 ha, with density stocking 4.15 ± 1.21 PL/m2. For prawns were harvested after over 8 months, the prawn yield was 421.08 ± 172.21 ton/ha/crop, the profit was 34.02 ± 14.02 million VND/ha/crop and the benefit ratio was 1.33 ± 0.56 times. The yield and the profits were affected by density stocking and nursing survival rate. Besides the advantages of labor resources, natural conditions, and ease and less risk of giant freshwater prawn culture; however, the system currently faces many difficulties, such as lower nursing survival rate, unguaranteed quality, and quantity of postlarvae, salinity intrusion, unstable product market. Therefore, in order to contribute to sustainable aquaculture development, the necessary solutions include (1) providing high quality and quantity of postlarvae; (2) using settling ponds to have active water; (3) building and improving infrastructure, and irrigation systems to prevent salinity intrusion; and (4) finding the product market.

In this work, we study the generation of a negative refractive index based on electromagnetically induced transparency (EIT) in a Rb four-level N-type atomic gas medium. We derive analytic expressions for the relative permittivity and relative permeability of the medium according to the parameters of the probe, pump, and signal laser fields. We then investigate the variation of the real parts of the relative permittivity and relative permeability with respect to the intensity and frequency of the pump and signal laser fields. In the presence of the pump laser beam, the medium becomes transparent to the probe laser beam even in the resonant region. At the same time, the real parts of the relative permittivity and relative permeability are simultaneously negative (i.e., the medium exhibits a negative refractive index) in the EIT spectral domain. In the presence of the signal laser beam, the EIT effect occurs over two different frequency domains of the probe beam, so a negative refractive index is also generated in these two frequency domains. The investigation of the real parts of the relative permittivity and relative permeability with intensity and frequency of the pump and signal laser fields allowed us to find the laser parameters for the appearance of the negative refractive index, which can be useful for experimental observations.

Mangan dioxit (MnO2) được tổng hợp trực tiếp trên nền graphen oxit (GO). Chúng tôi nghiên cứu quá trình khử điện hoá vật liệu α-MnO2/GO bằng hai kỹ thuật chính là von-ampe vòng (CV) và điện thế thời gian (i-T). Các mẫu vật liệu được đặc trưngằng phổ FT-IR, phổ Raman, diện tích bề mặt và phân tích tổng trở điện hoá. Cấu trúc α-MnO2 được xác định thông qua phổ FT-IR và phổ Raman tại các bước sóng kích thích dao động 507 và 642,5 cm–1. Vật liệu khử α-MnO2/ErGOCV và α-MnO2/ErGOi-T có tổng trở điện hoá thấp (0,188 và 0,147 kΩ) và diện tích bề mặt lớn gấp 1,7 lần so với vật liệu α-MnO2/GO. Các tính ưu việt của vật liệu composite α-MnO2/ErGO thúc đẩy khả năng chuyển điện tử và tăng cường hoạt tính xúc tác điện hoá của sensor oxy hoá khử trên bề mặt của điện cực đã được biến tính. Ở các điều kiện thí nghiệm thích hợp, phương pháp LS-AdCSV sử dụng điện cực biến tính α-MnO2/ErGO có thể áp dụng để phân tích đồng thời chloramphenicol và tinidazole. Hàm lượng chloramphenicol trong thuốc mỡ tra mắt xác định trên điện cực này có giá trị đúng với số liệu ghi trên nhãn.

Ở Việt Nam, kỹ thuật multiplex PCR đã được sử dụng để chẩn đoán nhiều bệnh trên vật nuôi nhưng kỹ thuật này hiện nay chưa được áp dụng để chẩn đoán bệnh trên cừu. Trong nghiên cứu này, chúng tôi đã phát triển một kỹ thuật multiplex PCR để phát hiện đồng thời hai tác nhân chính gây tụ huyết trùng trên cừu Phan Rang là Pasteurella multocida và Mannheimia haemolytica. Bằng cách sử dụng hai cặp mồi đặc hiệu, với nồng độ tối ưu của mỗi mồi là 5 pM, phương pháp này đã nhân thành công đoạn gen kmt1 từ P. multocida và gcp từ M. haemolytica trong cùng một phản ứng chứa hỗn hợp DNA tổng số của hai vi khuẩn này ở nồng độ thấp nhất là 0,1 ng mỗi loại. Thêm vào đó, phản ứng multiplex PCR này không bị ảnh hưởng bởi sự có mặt nhân tạo của một số DNA từ vi khuẩn khác. Đặc biệt, phương pháp multiplex PCR này có độ ổn định đạt 100% khi thử nghiệm trên quy mô nhỏ với 20 mẫu DNA thô thu được từ phương pháp xử lý nhiệt trực tiếp hay xử lý nhiệt sau khi làm giàu 10 mẫu thực địa. Đây là nghiên cứu đầu tiên ở Việt Nam về việc chẩn đoán tụ huyết trùng trên cừu bằng kỹ thuật multiplex PCR, kỹ thuật không chỉ có giá trị để phát hiện vi khuẩn P. multocida và M. haemolytica ở cừu mà còn có vai trò tham khảo để chẩn đoán những vi khuẩn này trong các đối tượng vật nuôi khác.

The dispersion characteristics of As2S3 solid-core photonic crystal fibers were investigated with the change of structural parameters including filling factor (d/Λ) and lattice constant (Λ). Photonic crystal fiber obtained diverse dispersion including all-normal and anomalous dispersion with two zero-wavelengths dispersion at all values of lattice constant investigated. The dispersion value increases when the lattice constant increases and the filling factor decreases. Photonic crystal fiber has a flat dispersion curve and closeness to the zero-dispersion curve in the longwavelength range are advantages of this design. Based on the analysis of numerical simulation results, we have proposed two structures with optimal dispersion for the application of supercontinuum generation.

This case study investigates the factors influencing customers’ unsecured loan decisions at financial institutions in Tra Vinh City. By collecting primary data from 224 customers in need of loans in Tra Vinh City and using quantitative data analysis methods, the study discovered five factors influencing customers’ unsecured loan decisions at financial institutions in Tra Vinh City: service quality, lending policy, consumer behavior, financial situation, and subjective standards, respectively. The authors propose policy implications based on the research findings to improve credit quality in Tra Vinh City.

Ca2Al2SiO7 (CAS) doped with Eu3+ and Dy3+ was successfully synthesised with the solid-phase reaction method, in which the sample was sintered at 1,280 °C for one hour. The energy-transfer phenomenon from Dy3+ to Eu3+ was observed in the CAS matrix. The optimal doping concentration of Dy3+ and Eu3+ is 1.5 and 1% mol. In addition, the energy-transfer mechanism, CIE colour coordinate, and CCT colour temperature of CAS/Dy3+/Eu3+ were also presented and discussed.

Centella asiatica (L.) Urb., belonging to the Apiaceae family, grows widely in shady, moist or marshy places. C. asiatica has been used in traditional medical systems in Asia for over 100 years. A better understanding of genetic diversity is essential for its conservation and use. In this study, we performed the genetic diversity analysis for 24 cultivars of Centella asiatica using 24 selected RAPD markers. There are genetic differences among the studied samples. However, the molecular screening with RAPD markers shows that genetic difference (0.0025–0.2194) and genetic diversity indices (%P = 42.02%, h = 0.1272, I = 0.1938) are relatively low. Besides, HUIB_CA06 and HUIB_CA26 (from Thua Thien Hue province) are genetically different from the remaining varieties, which warrants further analysis of these varieties.

By using a cross-sectional study, this study aimed to determine the ratio of occupational stress, stress levels and the relationship between stress status and social characteristics of the sample, factors at work, as well as how secondary school teachers respond to stress in Tra Cu District, Tra Vinh Province. The study conducted a survey to investigate 466 teachers currently teaching at 14 secondary schools in Tra Cu District, Tra Vinh Province, from May 2020 to June 2020. Research results showed that the percentage of teachers who suffered mild stress and severe stress was 18.9% and 8.1%, respectively. The signs of stress in teachers correlated with several factors such as job demand, work control and ways of coping at work. When the average score of the assessment “job demand” or “work control” increased by one point, the rate of stress on teachers was reduced by 23% (95% CI: 0.73 – 0.81) and 12% (95% CI: 0.84 – 0.93) respectively. By contrast, the average score of “confrontation” increased by one point leading to 3.21 times higher (95% CI: 2.61 – 3.96) possibility of causing stress. As well as the average score of "avoidance" increased by one point, the possibility of causing stress in teachers increased 3.03 times (95% CI: 2.45 – 3.74). The findings showed that mental health problems in teachers at secondary schools, in general and in Tra Cu District, Tra Vinh Province in particular, had not received sufficient attention. Therefore, the problems should be taken seriously not only by teachers school administration.

Liquified Petroleum Gas (LPG) fuel is currently an energy source being widely applied in many fields in Vietnam, making a significant contribution to the development of the national economy. This paper presents research results of applying LPG fuel used in motorbikes. The traditional liquid fuel system (gasoline) on a motorbike was replaced by an electronically controlled LPG fuel injection system. LPG fuel is designed to inject into the intake manifold. The injection quantity and injection timing are calculated and controlled by the electronic control unit through the calculation and analysis of the input of key parameters such as intake air pressure and temperature, throttle position, engine speed, and camshaft position. The testing results on real roads in an urban area show that the motorbike operates stably on flat and uphill roads. In addition, the cost of LPG fuel consumption is less than that of the gasoline fuel consumption.

In this work, the Prussian blue/g-C3N4 (PB/g-C3N4) composite was synthesized from Prussian blue and g-C3N4 via a simple method. The composite was characterized by using X-ray diffraction, Fourier-transform infrared spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The material’s photocatalytic performance was studied via the degradation of rhodamine B (RhB). The results show that the composite degraded RhB more than pristine Prussian blue under visible light after 60 min. This material is promising for organic waste treatment.

Tụ huyết trùng là một bệnh truyền nhiễm có thể gây thiệt hại nghiêm trọng cho chăn nuôi gia súc, gia cầm nếu không được chẩn đoán và điều trị kịp thời. Vì vậy, trong nghiên cứu này chúng tôi đã phát triển phương pháp PCR có độ nhạy, độ đặc hiệu và độ chính xác cao để phát hiện sự có mặt của vi khuẩn P. multocida, một trong những tác nhân gây bệnh tụ huyết trùng trên cừu Phan Rang. Gen KMT1 của vi khuẩn P. multocida được nhân lên bằng cặp mồi đặc hiệu FKMT1/RKMT1 ở nồng độ khoảng 104 bản sao của plasmid mang gen đích. Phản ứng PCR không bị ảnh hưởng khi có mặt DNA của một số vi khuẩn Gram âm khác như E. coli hay M. haemolytica. Đặc biệt, với phương pháp PCR, chúng tôi đã phát hiện sự có mặt của vi khuẩn P. multocida từ mẫu DNA thô thu được bằng xử lý mẫu vi khuẩn/mẫu dịch ngoáy mũi của cừu nghi nhiễm bệnh trong đệm TE chứa 0,1% TritonX-100 mà không cần tinh sạch DNA tổng số. Đây là nghiên cứu đầu tiên công bố một phương pháp xác định sự có mặt của P. multocida trên cừu Phan Rang và là cơ sở để xây dựng quy trình chẩn đoán hiệu quả nhằm góp phần kiểm soát bệnh tụ huyết trùng trên đối tượng này.