Ho Chi Minh City Open University Journal of Science
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Phân tích ngược hiệu chỉnh thông số độ cứng nền đất yếu bằng mô hình Hardening Soil cho bài toán hố đào sâu tại Thành phố Hồ Chí Minh
Get PDFIn Ho Chi Minh City, the growing demand for underground infrastructure development on soft clay foundations, particularly in areas such as District 2, District 7, and Nha Be, presents significant geotechnical challenges. A critical issue in deep excavation design is the accurate prediction of diaphragm wall displacements. While the Mohr-Coulomb model is commonly used in practice, it fails to capture the nonlinear and stress-dependent behavior of soft clays. The Hardening Soil (HS) model offers a more advanced alternative, though uncertainties remain in determining key input parameters, especially the reference stiffness modulus E50ref. This study conducts a back-analysis using the Plaxis 2D finite element program under the Undrained B assumption to calibrate the empirical correlation between the stiffness modulus reference E50ref and the undrained shear strength Su for typical soft clays in Ho Chi Minh City. The case study focuses on the Van Lang University Phase 4 project, where field measurements of wall displacement were obtained from 14 inclinometer locations. The results provide a suitable correlation E50ref = 500×Su, improving numerical prediction accuracy and supporting the optimization of deep excavation designs in complex soft soil conditions.Tại Thành phố Hồ Chí Minh (TP.HCM), nhu cầu phát triển hạ tầng ngầm trong điều kiện nền đất yếu ngày càng tăng, đặc biệt ở các khu vực như Quận 2, Quận 7 và huyện Nhà Bè. Một trong những thách thức kỹ thuật lớn trong thiết kế hố đào sâu là dự báo chính xác chuyển vị ngang của tường vây. Trong khi mô hình Mohr-Coulomb (MC) còn nhiều hạn chế khi áp dụng cho đất bùn sét yếu, mô hình Hardening Soil (HS) đã chứng minh tính hiệu quả nhờ khả năng mô phỏng phi tuyến và phụ thuộc ứng suất. Tuy nhiên, việc xác định các thông số đầu vào, đặc biệt là môđun đàn hồi tham chiếu E50ref vẫn còn nhiều bất định. Nghiên cứu này thực hiện phân tích ngược trên phần mềm Plaxis 2D với giả thiết không thoát nước loại B (Undrained B), nhằm hiệu chỉnh tương quan thực nghiệm giữa môđun đàn hồi tham chiếu E50ref và sức kháng cắt không thoát nước Su cho lớp bùn sét yếu đặc trưng tại TP.HCM. Công trình nghiên cứu là dự án Trường Đại học Văn Lang - Giai đoạn 4, với số liệu quan trắc chuyển vị từ 14 vị trí bằng Inclinometer. Kết quả nghiên cứu đề xuất công thức tương quan E50ref = 500×Su, góp phần nâng cao độ chính xác mô phỏng và tối ưu thiết kế công trình ngầm trong điều kiện địa chất phức tạp
Anti-oxidant and anti-bacterial effects of Diospyros kaki leaf extract in Vietnam
Get PDFDiospyros kaki is a famous commercial plant with its edible fruit (persimmon) and is widely used as a traditional remedy in Vietnam. However, the anti-oxidant and anti-bacterial effects against gastrointestinal microbes of the D. kaki leaf extract have not been elucidated yet. In this study, the methanol extract from
D. kaki leaves contained some chemical groups, such as tannins, flavonoids, phenolic compounds, alkaloids, and saponins, mainly it was rich in polyphenols and flavonoids (528.11 ± 12.96 mg GAE/g and 44.49 ± 6.77 mg QE/g, respectively). The extract exhibited a strong anti-oxidant ability (DPPH scavenging activity of about 91.83 ± 1.02% and total anti-oxidant capacity of approximately 110.58 ± 2.65 mg AAE/g). Furthermore, the anti-bacterial activity of the extract against some gastrointestinal bacteria, including Staphylococcus aureus, Enterococcus durans, Enterococcus faecium, and Yersinia enterocolitica, has been reported for the first time (the zone of inhibition ranging from 14.17 - 24.67mm).
MIC of the extract was 0.6125 - 1.25 mg/mL, and MBC was
2.5 - 5 mg/mL, which implied the extract exerted a bactericidal effect. These findings suggest D. kaki leaf extract is a promising source of extracting bioactive compounds, such as anti-oxidant and anti-microbial agents, and a potential medicine for the treatment of gastrointestinal infections
Analysis of growth curves and morphological characteristics of some commercial Scoby strains
Get PDFKombucha Tea (KT) is a product of fermentation by a microbial system, with many different names such as ginseng tea, mushroom tea, Kargasok tea, or Manchurian tea. KT products have recently become popular because they bring many health benefits to users (Jayabalan et al., 2014). The present study surveyed the growth curves of three commercial SCOBY strains (SB1, SB2, and SB3) to evaluate their adaptability and development in the tea epidemic environment. The results showed that all three strains of SB1, SB2, and SB3 had significantly different microbial growth rates and levels. SB1 has the highest growth rate and the highest microbial density (8.6 × 10⁷ CFU/mL), indicating rapid adaptability and good fermentation performance. The results of the study contribute to providing an essential scientific basis for the selection and application of suitable SCOBY lines in Kombucha production, and at the same time help to optimize fermentation conditions to improve product qualit
Assessing the adoption and impact of construction automation technologies on project management efficiency: A case study of Cebu City
Get PDFThis study rigorously assessed the adoption and impact of construction automation technologies on project management efficiency within the urban infrastructure context of Cebu City, Philippines. Grounded in the Technology Acceptance Model (TAM), the research examined the influence of three key constructs; Perceived Usefulness (PU), Perceived Ease of Use (PEOU), and Behavioral Intention to Use (BIU) on the integration of automation technologies, including Building Information Modeling (BIM), Artificial Intelligence (AI), and the Internet of Things (IoT). Utilizing a quantitative-descriptive and correlational design, data were collected from 40 purposively selected construction professionals through validated survey instruments. Statistical analyses included descriptive statistics, Pearson’s correlation, and internal consistency testing via Cronbach’s Alpha. The findings revealed that only PEOU exhibited a statistically significant relationship with the level of influence of automation adoption. At the same time, PU and BIU did not demonstrate significant associations with project management efficiency or procedural effectiveness. This outcome suggests that external structural barriers, such as regulatory gaps, limited financial capacity, and inadequate workforce readiness, remain significant impediments to the implementation of automation. Despite favorable perceptions of automation’s utility in enhancing coordination, cost estimation, and real-time monitoring, actual usage remained suboptimal. The study concluded that construction automation can substantially contribute to improved project management efficiency if institutionalized through policy incentives, standardized digital frameworks, and comprehensive workforce upskilling programs. These findings offered critical implications for stakeholders seeking to accelerate digital transformation in the Philippine construction sector. They proposed directions for future research focused on automation, scalability, and BIM compliance enforcement across varying firm sizes
Automated customer consultation system for Pastry Shops
Get PDFAutomated customer consulting is a form of automated customer care and consulting that utilizes texting and chat functions to replace human interaction. This research improves the Bi-LSTM language model. We aim to enhance the accuracy and applicability of an automated customer consultation system, which may impact enterprises and traders. Our question-answer system uses querying the entity and model textual similarity to match models. Automated customer care systems utilize computers or other technologies to assist customers. It empowers clients to address problems without human assistance in customer care. Human resources can address complex requests or high-value consumers, as automation handles many repetitive and straightforward activities. Many firms utilize it, especially fast-growing ones that need to arrange support
Evaluation of the anti-inflammatory activity of the rhizome essential oil of Distichochlamys citrea
Get PDFDistichochlamys citrea, an endemic plant native to central Vietnam, holds significant ethnomedicinal value in Vietnamese herbal medicine. Although the essential oil derived from the rhizome of D. citrea is known for its bioactivities, including antibacterial and antioxidant properties, its anti-inflammatory potential has not been extensively explored yet. In this study, the anti-inflammatory effect of the essential oil has been comprehensively evaluated from in silico to in vivo studies. A molecular docking study revealed that cineole, neral, and geranial, three main components of the essential oil, were capable of forming promising interactions with 5-lipoxygenase and inducible nitric oxide synthase (ranging from -4.7 to -6.3 kcal/mol). Furthermore, the essential oil exhibited a strong inhibitory effect against protein denaturation (86.67%, 100 µg/mL). In the carrageenan-induced paw edema model, the essential oil (4%) could inhibit 32.83% of paw edema as compared to the NaCl-treated group. Collectively, these findings position the essential oil extracted from rhizomes of D. citrea as a novel candidate for the development of anti-inflammatory medicine
Mitigating output DC current ripple in a three-phase current source rectifier using an optimized space vector modulation
Get PDFThe mitigation of output DC ripple in three-phase current source rectifiers represents a significant design challenge, directly impacting the quality of the delivered power. To address this issue, this paper introduces a novel control framework based on the concept of Virtual Space Vector (VSV) modulation. The fundamental operating principle of the proposed strategy is to systematically reduce the dwell time of the active vector with the largest magnitude within each control sector. This principle is realized through a two-fold process. First, a set of virtual vectors is constructed, with each being a linear combination of two adjacent active switching vectors. Second, within every switching period, the desired current reference vector is synthesized not by the original active vectors, but by a combination of two neighboring virtual vectors and a zero vector. Comprehensive simulation results corroborate the effectiveness of this approach in attenuating DC-link current ripple
Understanding the factors influencing the human development index of Asian nations using path analysis
Get PDFThis study explores the factors influencing the Human Development Index (HDI) in Asian nations, focusing on Gross National Income (GNI) and the Gender Development Index (GDI) as key determinants. Using path analysis, the research analyzes secondary data from the United Nations Development Programme (UNDP) Human Development Report for 2021 - 2022. The findings indicate that GNI (economic growth) and GDI (gender equality) have significant positive impacts on HDI, emphasizing the importance of economic prosperity and gender parity in fostering human development across Asia. Grounded in Amartya Sen’s capability approach, which prioritizes individual freedoms and choices, the study suggests region-specific policies. These include promoting economic diversification strategies tailored to emerging economies, enhancing technology and service sectors in middle-income countries, and expanding vocational training programs in lower-income nations to address skills gaps. For countries with significant gender disparities, robust policies that ensure equal access to education and employment for women are recommended. Additionally, prioritizing maternal and child healthcare improvements, particularly in less developed regions, can elevate overall well-being. By adopting these targeted strategies, Asian countries can achieve sustainable human development, creating societies where all individuals can lead fulfilling lives
Green engagement pathways in tourism: The converging roles of knowledge sharing and social media in shaping revisit intentions
Get PDFDespite significant advances in green marketing within the tourism sector, the specific pathways through which green knowledge sharing influences tourist behaviors and revisit intentions remain underexplored. This study addresses this gap by examining how the dissemination of environmentally-focused knowledge by organizations impacts tourists’ environmentally responsible engagement behaviors and their intentions to revisit, with a particular focus on the moderating role of social media usage. Utilizing a mixed-methods approach in Vietnam’s burgeoning tourism industry, data from 700 tourists were analyzed using structural equation modeling to validate hypothesized relationships. The results indicate that environmentally responsible engagement behaviors significantly mediate the relationship between organizations’ green knowledge dissemination and tourists’ intentions to revisit destinations. Moreover, the study finds that active engagement on social media platforms intensifies this mediation effect, suggesting that strategic digital interactions can amplify the influence of green knowledge on tourist behaviors. This research contributes to the sustainable tourism literature by demonstrating how social media can enhance the effectiveness of green marketing strategies, promote sustainable practices, and improve long-term business sustainability in the tourism sector
The relationship between host country factors and FDI motivations: Evidence from Korean FDI in ASEAN countries
Get PDFThe literature suggests that various host country factors influence firms’ decisions to invest abroad, but there is a low consensus in empirical research, as results vary across contexts. However, empirical studies typically examine the relationship between overall FDI and host country factors, ignoring the differences in investment motivations of multinational enterprises. Firms may have different motivations, such as market seeking or efficiency seeking, and thus are attracted by other factors in host countries. Using data from the Korean Export-Import (EXIM) Bank and fixed-effect models, this study examines how the determinants of FDI vary based on different investment motivations from South Korea to nine ASEAN countries (excluding Brunei). Economic growth deters low-wage-seeking and resource-seeking FDI but does not impact other FDI motivations. However, some factors commonly believed to influence specific motivations affect FDI similarly across motivations. For example, GDP and wages consistently emerge as determinants across different types of investment. Our findings thus contribute to the literature on the determinants associated with various FDI motivations. However, as our study covers a limited set of host country factors and is focused on a specific context, further and more comprehensive investigations are needed in the future