University of Da Nang

• Investigating the settlement of high embankments under HSR train loads. • Applying an advanced simulation model by Plaxis API with Python remote scripting. • Developing a reliable settlement estimation using the GEP algorithm. • Optimising the design of the GRPS system with geocell reinforcement. The construction of high-speed railway (HSR) embankments on soft ground areas is a geotechnical challenge due to excessive settlement and long-term deformation. Thus, this study evaluates the effectiveness of deep cement mixing (DCM) piles reinforced by a geocell system (GPRS) as a ground improvement method. An advanced automated simulation framework using Python remote scripting was developed to examine the effects of train load, embankment height, soft soil thickness, and the number of geocell layers. Approximately 336 data points on the settlement of the HSR embankment was extracted from Plaxis analysis. The highest equivalent train load was 100 kN/m 2 and the settlement of the embankment fluctuated from 22 to 65 mm. A Gene Expression Programming (GEP) algorithm was then applied to develop a reliable regression among the key variables with high accuracy (R = 0.99) and low errors. The parametric study indicated that the geocell reinforcement could significantly improve the lateral resistances, mobilise the membrane effect within the fill material, and reduce vertical stress and cumulative settlement. The research findings provide critical insights for improving the design process, optimising GRPS reinforcement using geocell, and enhancing predictive capabilities for HSR embankment settlement under various ground conditions.

Biến đổi khí hậu và thiên tai khiến Việt Nam đối mặt với nhiều rủi ro nghiêm trọng, đe dọa phát triển bền vững. Trong bối cảnh đó, việc tăng cường năng lực ứng phó và huy động hỗ trợ quốc tế trở nên cấp thiết. Bài viết đánh giá vai trò của Nhật Bản - nhà tài trợ ODA song phương lớn nhất của Việt Nam trong giảm nhẹ rủi ro thiên tai và thích ứng biến đổi khí hậu. Sử dụng các phương pháp phân tích – tổng hợp tài liệu thứ cấp, so sánh, nghiên cứu chính sách và nghiên cứu trường hợp, bài viết cho thấy ODA Nhật Bản đóng góp đáng kể trong nâng cấp hạ tầng phòng chống thiên tai, chuyển giao công nghệ dự báo, đào tạo nhân lực và thúc đẩy quản trị rủi ro tổng hợp, song xu hướng giảm viện trợ không hoàn lại và điều kiện vay chặt chẽ hơn đặt ra nhiều thách thức. Bài viết góp phần cung cấp cơ sở khoa học cho việc hoạch định chính sách, tối ưu hóa hợp tác ODA trong bối cảnh Việt Nam bước vào giai đoạn phát triển mới.

Nghiên cứu này phân tích tác động của công nghiệp hóa (CNH), đô thị hóa (ĐTH), du lịch và chất lượng thể chế (PCI) đến tăng trưởng kinh tế tại 11 tỉnh miền Trung Việt Nam giai đoạn 2009-2024. Sử dụng mô hình hiệu ứng cố định với sai số chuẩn Driscoll-Kraay (FE-DKSE), nghiên cứu xử lý đồng thời hiện tượng phương sai thay đổi, tự tương quan và phụ thuộc chéo trong dữ liệu bảng vùng. Kết quả cho thấy, CNH và ĐTH đều có tác động tích cực, trong đó CNH giữ vai trò trụ cột, còn ĐTH hỗ trợ phân bổ nguồn lực và mở rộng thị trường. Du lịch được xác nhận là động lực bổ sung nhưng hiệu quả giảm dần khi mức độ ĐTH tăng cao. PCI góp phần cải thiện môi trường kinh doanh song chưa tạo ra hiệu ứng ngưỡng rõ rệt. Phát hiện này nhấn mạnh sự cần thiết của chiến lược phát triển tích hợp CNH-ĐTH gắn với du lịch và cải thiện thể chế, nhằm hướng tới tăng trưởng bền vững tại miền Trung.

Abstract The performance of youth in martial arts arises from complex interactions among anthropometric, neuromuscular, maturational, and cognitive elements. However, it is uncertain whether these performance variables constitute common or discipline-specific latent structures across different martial arts. The study aimed to identify discipline-specific latent performance characteristics in youth martial arts athletes and the influence of anthropometric, neuromuscular, maturational, and cognitive factors on inter-sport variation. One hundred fifteen (n = 115) trained male athletes (age 14.4 ± 1.7 years) from judo, jujitsu, Muay Thai, wrestling, taekwondo and pencak silat underwent standardized evaluations. Principal Component Analysis with Varimax rotation (eigen values ≥ 1.0) showed distinctive component structures for each discipline. The primary component for the entire cohort accounted for 38.4% of the variance, predominantly influenced by skeletal muscle mass (0.91–0.94) and countermovement jump peak force (0.90–0.92), suggesting a common morphology–power basis. Judo, Muay Thai, wrestling, and pencak silat exhibited strength profiles characterized by substantial mass support and forceful grasping and striking with a variance ranging from 30.4% to 45.3%. Taekwondo presented a power-centric framework propelled by explosive lower-limb strength (loadings: 0.96–0.99), while jujitsu revealed a cognitive-motor profile, with inhibitory control and executive processing accounting for 60.3% of the variance. The youth performance in martial arts is supported by a common morphological and power foundation, alongside discipline-specific neuromuscular and cognitive requirements.

This paper presents an extremely high step-up DC-DC converter using a quadratic topology and a coupled inductor (CI). The proposed converter (PC) utilizes a single switch, simplifying the control strategy and reducing switching losses. A passive clamp circuit recycles leakage energy, reducing voltage stress (VS) on the MOSFET and enabling the implementation of a low on-state resistance switch for higher efficiency. Additionally, the quadratic structure and passive clamp circuit contribute to higher voltage gain (VG) and better performance. The converter’s operating principles, steady-state analysis, and component selection criteria are discussed in detail. The influence of magnetizing inductance, duty cycle, and parasitic components on the VG is also investigated, along with the system’s dynamic response under input voltage and load variations to ensure stable operation. A comparative evaluation with existing converters highlights its advantages. The PC is verified through SIMPLIS simulations, where key performance metrics such as VG and switching stress are analyzed. Furthermore, a hardware prototype with a power rating of 300 W is built to confirm the theory and showcase the converter’s performance. Experimental results demonstrate high efficiency, stable operation, and substantial VG, validating the converter’s feasibility for renewable energy systems (RES).

Microalgae cultivation is currently constrained by two major techno-economic bottlenecks: poor gas-liquid mass transfer and high harvesting costs. This review examines micro-nanobubble (MNB) technology as a strategic solution to address these barriers. Owing to characteristics such as high internal pressure, prolonged residence time, and colloidal stability, MNBs significantly enhance the volumetric mass transfer coefficient ( ) while minimizing hydrodynamic shear stress. Case studies demonstrate that MNBs not only increase biomass productivity but also facilitate efficient flotation-based harvesting with low energy consumption (below 0.5 kWh·kg⁻¹ of dry biomass), while simultaneously improving nutrient removal in wastewater. Despite remaining challenges in scaling up, this technology offers a promising pathway for integration into circular economy models, driving the commercialization of microalgae for biofuels and high-value products.

Abstract This study investigates the water absorption behaviour of binderless materials from lignocellulosic fiber resources under varying relative humidity (RH) conditions. The desiccator method utilized saturated salt solutions including sodium chloride (NaCl), and potassium nitrate (KNO 3 ) to establish contrilled RH environments of approximately 75 and 95%, respectively. Water absorption was measured gravimetrically at the state of equilibrium, and the relationship between moisture content levels and RH was examined. Results showed a nonlinear increase in water absorption with higher RH, reflecting the hygroscopic nature of the fibrous materials. An analytical model was proposed to describe this sorption isotherm, and its predictions showed good agreement with experimental data. Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed to determine the function groups contributing to moisture sensitivity. Additionally, thermal resistance capacity was also examined in relation to increased relative humidity. The findings from the current study provide valuable insights into the hygrothermal performance of binderless lignocellulosic materials, supporting their potential application in sustainable building materials where humidity control and durability are critical.