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Mechanical behavior of functionally-Graded concrete beam under flexural loading
Số 87 - Số Tiếng Anh (12/2023)
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trang 02-08
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Tải về (500.41 KB)
Nguyen Viet Duc
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Tóm tắt
This paper presents the mechanical behavior of functionally-graded concrete (FGC) beam under flexural bending. The FGC beam was made of conventional concrete of strength class 30MPa with a thickness of 45mm and high performance glass fiber reinforced concrete (HPGFRC) of strength class 60MPa with thickness of 15mm. While the reference beam is composed of entirely conventional concrete of strength class 30MPa with thickness of 60mm. Both of the beams were reinforced by using two steel bars at the bottom with a concrete cover of 25 mm. Based on the third-point bending test, both the reference and FGC beam behaved in a similar manner, even though the latter consists of two layers of conventional concrete and HPGFRC. Their mechanical behavior is represented in four stages including the first crack propagation, the second crack appearance, reinforcement load-carrying capacity, and finally failure. Cracking and ultimate strength obtained from the FGC beam were 19% and 28% higher than those from the reference beam. The better performance of the FGC beam was mainly due to the functionality of HPGFRC with higher strength and glass fiber inclusion. By observing the failure of the FGC beam, there is no crack or delamination between the conventional concrete and HPGFRC layers on this beam.
Keywords: Functionally-graded concrete, flexural loading, glass fiber, high performance glass fiber reinforced concrete |
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Mechanical-microstructural characteristics of concrete containing high volumes of coal bottom ash
Số 87 - Số Tiếng Anh (12/2023)
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trang 09-15
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Tải về (2077.65 KB)
Nguyen Van Dung*, Mai Thi Hong, Nguyen Thi Thanh, Nguyen Vu Linh
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Tóm tắt
This paper aims to study the effect of coal bottom ash (CBA) as a fine aggregate substitution at high levels on the mechanical properties and microstructure characteristics of concrete. CBA that sourced from a local coal-fired power plant in Vietnam was used to replace the natural sand (NS) in the concrete mixtures at different levels of 0, 30, 50, 70, and 100%. The concrete samples were prepared in the laboratory and checked for properties through the tests of compressive strength (CS), ultrasonic pulse velocity (UPV), water absorption (WA), porosity, electrical surface resistivity (ESR), and thermal conductivity (TC). Notably, the scanning electron microscope was also used to characterize the microstructure of the hardened concrete. Test results show that the replacement of NS by CBA affected the concrete’s properties significantly. However, all of the concrete samples were classified as good quality with the UPV, CS, WA, porosity, ESR, and TC values fell within the ranges of 4176 – 4636 m/s, 11.3 – 25.9 MPa, 2.89 – 7.02%, 5.11 – 10.19%, 5.21 – 10.55 kΩ.cm, and 1.17 – 1.72 W/mK, respectively. Therefore, the proper quantity of CBA will be suggested depending on the requirement for the quality of the concrete for a specific application.
Keywords: Concrete, coal bottom ash, mechanical property, durability, microstructure |
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A study of flow structure, drag force, and particle tracking through many circular cylinders
Số 87 - Số Tiếng Anh (12/2023)
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trang 16-24
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Tải về (984.50 KB)
Vu Huy Cong
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Tóm tắt
The variation of multiple circular cylinders' drag coefficient was investigated using numerical methods. Moreover, the particle tracking simulation was also performed to show the flow structure and how particles move inside the cylinder array. It was found that the density and location of cylinders have a significant influence on the fluid forces, flow structure, and particle movement inside them. The results showed that when the number of cylinders increases per unit area, the total drag coefficient increases but the average drag coefficient per cylinder decreases. A functional relationship between the drag coefficient and the density of cylinders was determined. The distribution or position of the cylinders has a considerable impact on particle distribution. The cylinders in the staggered arrangement disperse the particles more in a fan-shaped manner, spreading them out in the cylinder array. The results will advance knowledge of the drag force and flow field, particularly in matter propagation or dispersion through systems of objects.
Keywords: Drag fore coefficient, cylinder, particle tracking, flow structure |
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Tire-road separation: Problem and solving method
Số 87 - Số Tiếng Anh (12/2023)
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trang 25-30
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Tải về (985.80 KB)
Nguyen Dang Quy, Vu Ngoc Tuan*, Nguyen Truong Sinh, Vu Van Tan
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Tóm tắt
The paper discusses the movement of a quarter-car concerning whether the tires are in contact with the road or not. A set of equations is formulated to highlight the two different states, and a new approach is presented to solve these equations while also considering the separation of the tires. A comparison between the new and old models shows that previous studies lacking this consideration must be reevaluated. A simulation is conducted to demonstrate how the characteristics of the road and suspension affect vertical displacement. Ultimately, this research provides more accurate outcomes that can be used to inform future suspension design.
Keywords: Quarter-car vibrations, vehicle vibrations, vibration dynamics, tire-road separation, vehicle safety, ride comfort |
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Tensile–shear response correlation of ultra-high-performance fiber-reinforced concrete at high strain rates
Số 87 - Số Tiếng Anh (12/2023)
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trang 31-38
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Tải về (455.21 KB)
Tri Thuong Ngo*, Cong Bang Phan
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Tóm tắt
The superior mechanical characteristics of ultra-high-performance fiber-reinforced concrete (UHPFRC) hold great potential for application in structures subjected to extreme loads, such as impacts or blasts. However, the practical application of this material in engineering is limited due to a lack of information about its mechanical properties, especially at high strain rates. In this study, the shear behavior of UHPFRC was investigated using a novel shear test setup installed in the universal testing machine (UTM) for static tests and the improved-strain energy frame impact machine (I-SEFIM) for high strain rate tests, respectively. Additionally, effect of fiber volume contents and the correlation between shear and tensile behavior were also clarified. The experimental results indicated a significant increase in the shear strength of UHPFRC as the fiber volume content and applied strain rates increased, even though the shear strain rate sensitivity was not as high as the tensile strain rate sensitivity. The shear-tensile ratios were approximately 1.45, 0.67, and 0.66 at average strain rates 0.000667, 99, and 184 s-1, respectively.
Keywords: UHPFRCs, shear resistance, tensile resistance, high-strain rates |
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Double Deep Q-Network algorithm for solving traffic congestion on one-way highways
Số 87 - Số Tiếng Anh (12/2023)
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trang 39-46
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Tải về (601.69 KB)
Nguyen Tuan Thanh Le*, Dat Tran-Anh, Quoc-Bao Bui, Linh Manh Pham
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Tóm tắt
The problem of reducing traffic congestion on highways is one of the conundrums that the transport industry as well as the government would like to solve. With the great development of high technologies, especially in the fields of deep learning and reinforcement learning, the system using multi-agent deep reinforcement learning (MADRL) has become an effective method to solve this problem. MADRL is a method that combines reinforcement learning and multi-agent modeling and simulation approaches. In this article, we apply the Double Deep Q-Network (DDQN) algorithm to a multi-agent model of traffic congestion and compare it with two other algorithms.
Keywords: Traffic congestion problem, multi-agent deep reinforcement learning, agent-based simulation, autonomous vehicles |
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Application of deep learning in water surface detection for Dong Hoi city using Sentinel-1 images
Số 87 - Số Tiếng Anh (12/2023)
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trang 47-55
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Tải về (780.93 KB)
Nguyen Cam Van, Dinh Viet Tu, Van Ngoc An, Dinh Nhat Quang*
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Tóm tắt
Efficient water resource management is a critical mandate for governmental authorities, as it directly impacts the effective utilization of this invaluable natural resource. The expeditious and accurate extraction of water surfaces significantly impacts governmental decision-making. Leveraging the advanced capabilities of high-resolution satellite imagery and the precise orbital data return, this study employs state-of-the-art deep learning techniques to enhance the efficiency of water surface detection. Specifically, Sentinel-1 data acquired from Google Earth Engine is utilized as a primary input for proposed machine-learning models. With the satellite images covering the entire of Quang Binh province, the analysis detects 15.96 km of water surfaces along the Nhat Le River and 2.8 km2 surface area of the Phu Vinh reservoir. The evaluation metrics, i.e., Overall Accuracy and Kappa, approach 0.9 approximately, indicate the robustness and potential of the results.
Keywords: Deep learning, Dong Hoi city, Google Earth Engine, Sentinel-1, water surfaces |
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Iot for sustainable water and wastewater management system - Case study in Bac Hung Hai irrigation and drainage system
Số 87 - Số Tiếng Anh (12/2023)
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trang 64-70
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Tải về (333.02 KB)
Nguyen Thu Hang
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Tóm tắt
The Bac Hung Hai Irrigation System (BHH IS) is a crucial component of Vietnam's agricultural sector, providing irrigation for various crops, livestock, aquaculture, and domestic activities. This is primarily due to capacity limitations, inadequate infrastructure, and decentralization of water management. This study conducted a survey, collected and analyzed data to identify the water pollution problem and the situation of the operation and management of the Bac Hung Hai irrigation system. From literature review and water polution management practices from other countries with similar conditions, IoT solution and proposed main system for implementing real-time observation and controlling of water quality are recommended to improve the water pollution problem and water management in BHH IS.
Keywords: Sustainable water, waste water management, Iot, sensors, irrigation system |
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Interactive effects of temperature and cu on distinct life stages of common tropical copepod across generations
Số 87 - Số Tiếng Anh (12/2023)
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trang 71-79
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Tải về (432.01 KB)
Pham T. Hong*, Hoang Bao Linh, Nguyen Thuy Duong, Le Thi Thanh Tra
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Tóm tắt
The tropical water environment faces increasing exposure to temperature extremes and contaminants stemming from human activities. Elevated temperatures and pollution levels in rivers and ponds have the potential to induce cumulative impacts on the diversity of aquatic ecosystems. However, the combined effects of these environmental changes on the life cycle of the Eucyclops euacanthus copepod, a bioindicator of aquatic ecosystem remain understudied. Our investigation delved into the direct and cross-generational impacts of very low copper concentration (50 µg/l) on the F0 and F1 generations of the common tropical copepod Eucyclops euacanthus under not extreme temperatures (24, 28, and 30 °C). In the F0 generation, Cu exposure did not alter the life cycle period of the copepod at 24 and 28°C, but an extension was observed at 30 °C. This lengthening of the life cycle at 30 °C in F0 copepods indicates a heightened energetic demand. In the F1 generation, the life cycle period was elevated in Cu-exposed F0 and at 34 °C. Notably, eggs from Cu-exposed F1 copepods at 30 °C failed to hatch successfully. These findings underscore the high vulnerability of tropical copepods to the combined effects of contaminants and temperatures in the contest of climate change effects on the water ecosystem.
Keywords: Tropical copepod, life-history traits, thermal effects, climate change, metal effects |
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Enhance removal of hospital wastewater-contaminated antibiotics by H2O2/S2O82-/ZVI process
Số 87 - Số Tiếng Anh (12/2023)
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trang 80-87
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Tải về (306.60 KB)
Hoa Thanh Nguyen*, Nguyen Thi Phuong, Nguyen Thi Lien
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Tóm tắt
The study indicates efficiency of antibiotics: Amoxicillin (AMX) and ciprofloxacin (CIP) removal in hospital wastewater using H2O2/S2O82-/ZVI process. Application of Box – Behnken design was to determine the experiment's effects on COD removal. Effect of pH, H2O2, S2O82-, ZVI and reaction time as independent variables in batch oxidation experiments, namely quadratic response. The predicted value of COD removal at optimum conditions (pH=5, [H2O2]=14.90 µg/L, [S2O82-]=50 mg/L, ZVI=40 mg/L and reaction times: 42.92 min) were 84.97%±1.6%. The AMX and CIP removal efficiencies were 99.95% and 99.90% within 42.92 minutes, while 47.60% COD occurred within 120 minutes. As a consequence, H2O2/S2O82-/ZVI process is an efficient and emerging method for removing antibiotics in hospital wastewater.
Keywords: Hospital wastewater, antibiotics, advanced oxidation process, zero-valent iron |
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A physically-based model for streaming potential in fully saturated porous media
Số 87 - Số Tiếng Anh (12/2023)
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trang 88-95
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Tải về (312.04 KB)
Nguyen Manh Hung, Nguyen Van Nghia, Luong Duy Thanh*
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Tóm tắt
The streaming potential that originates from water flow in porous media plays an important role in geophysical applications since it is sensitive to groundwater flow. In this work, we develop a physically-based model for the streaming potential in porous media using a bundle of capillary tubes model. The model is expressed in terms of microstructure properties, fluid properties and physicochemical properties at the fluid-solid interfaces. Additionally, we obtain an expression for the characteristic length scale as a function of microstructure properties. The model is successfully validated by comparisons with 12 samples of uniform glass bead available in literature. The model proposes a simple way to model the streaming potential generation in porous media under fully saturated conditions.
Keywords: Streaming potential, porous media, capillaries, pore size distribution |
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