Journal of Science and Technique
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RESEARCH ON THE APPLICATION OF GRATING PLATE AS BRIDGE DECK SLAB IN BAILEY QUICK ASSEMBLY BRIDGE
Get PDFThis article presents the calculation of the bearing capacity of the light-weight deck slab assembled from grating plates. The author uses the software SAP2000 on the basis of the finite element method to test the strength of this deck slab under the load of vehicles. From there, conclusions are drawn to build a scientific basis to determine the possibility of using grating plates as deck slabs for quick-assembled bridges serving security, defense, and rescue missions
SYNTHESIS AND CHARACTERIZATION OF γ-Al2O3@MgO SORBENT FOR EFFICIENT Pb REMOVAL FROM AQUEOUS SOLUTIONS
Get PDFThis study focuses on enhancing the adsorption capacity for lead ions by introducing MgO onto the surface of γ-Al2O3, forming γ-Al2O3@MgO. The γ-Al2O3 nanoparticles were synthesized via the sol-gel method on a citrate template. MgO was incorporated onto the surface of the γ-Al2O3 nanoparticles, with varying MgO concentrations (5%, 10%, and 15% by weight), achieved through the absorption of magnesium ions onto the material's surface followed by sintering at 773K. The findings indicated that both the γ-Al2O3 and MgO crystalline phases exhibit a cubic structure (Fd3m symmetry group), which is formed within the sample. Although the specific surface area diminished from 166 m2/g to 135 m2/g, the surface basicity increased proportionally to the amount of MgO incorporated into the sample. The impacts of various absorption conditions such as pH, adsorbent mass, and contact time on the Pb2+ ion adsorption capacity was systematically examined. Optimal conditions (pH=7, adsorption time of 8 hours) highlighted that the γ-Al2O3 material containing 10% MgO by weight showcased the highest Pb2+ adsorption capacity at 145 mg/g, surpassing the adsorption capacity of 135 mg/g for the γ-Al2O3 material
EXAMINING THE PHASE COMPOSITION OF TiO2 NANOPARTICLES DERIVED FROM SOL-GEL: IMPACT OF REACTION AND PROCESSING CONDITIONS
Get PDFTiO2 nanoparticles with crystallite size less than 15 nm were prepared from TiCl4 precursor by a modified sol-gel route. As-prepared TiO2 nanoparticles were extensively characterized using X-ray diffractometry, and their crystallite size was calculated using Debye-Scherrer formula. The phase composition and crystallite size of TiO2 nanoparticles were dependent on reaction parameters including TiCl4 concentration, reaction temperature, annealing temperature, and surfactant. The crystallite size increases with increasing annealing temperature. Amorphous-anatase phase transition occurs at 400-450oC and anatase-rutile phase transition occurs at ca. 700oC
PREDICTION OF THE SLUMP AND STRENGTH OF HIGH STRENGTH CONCRETE USING RANDOM FOREST MODEL
Get PDFRandom Forest (RF) has been successfully applied to a variety of engineering problems due to its simplicity, versatility, and suitability for both classification and regression tasks. Concrete, as a material composed of multiple complex elements, is influenced by numerous factors, posing challenges in accurately predicting its properties. In this article, an RF model is developed in predicting the slump and strength of concrete using mixed mineral admixtures from blast furnace slag and silicafume. The criterions to evaluate the accuracy of the models are the R squared (R2 ) and the root mean square error (RMSE). Comparing the predicted data with the tested data, the result indicates that RF model should be used in predicting both the slump and strength of concrete
STUDYING THE FLOOD REGULATION CAPACITY OF THE RED RIVER UPSTREAM RESERVOIR TO OVERCOME INCIDENTS AT LIEN MAC DYKE
Get PDFThis article presents a study on the flood regulation capacity of the upstream reservoirs of the Red River. One and two-dimensional numerical analyses have been carried out to simulate the hydraulic flow of the upstream reservoir and the downstream river network. The effectiveness of flood mitigation in a number of reservoi capacity scenarios have been estimated. Calculation results show that, the capacity of reservoirs of 5,553 million m3 would likely reduce the the flooded downstream area by 47,528 ha in case using a part of the capacity of the construction. The time when the reservoirs completely close the floodgates without discharging water to the downstream is from 27 to 30 hours, which is adequate for the Lien Mac dyke to be completely rectified within 24 hours
SYNTHESIS AND ELECTROCHEMICAL CHARACTERISTICS OF ZINC-DOPED SODIUM MANGANESE OXIDE AS A CATHODE MATERIAL FOR SODIUM-ION BATTERIES
Get PDFIn this article, zinc-doped sodium manganese oxide (NZMC) was synthesized by a conventional solid-state reaction method. Structure and morphology of the NZMC material were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS). The results show that Zn was successfully doped into the sodium manganese-based oxide (NMC) material. The NZMC material was utilized as a cathode material in CR2032-type coin cells for testing its electrochemical characteristics. The NZMC material had a superior initial discharge capacity of 155 mAh.g-1 between 1.5-4 V at a current density of 0.1 C. The capacity remained at 100 mAh.g-1 after 50 cycles. The results suggest that the NZMC material is a promissing cathode for sodium-ion batteries
Determination of radio wave propagation conditions in the atmosphere of Hanoi using the meteorological data
Get PDFThis article uses the data of radio occultation and the radiosonde data to determine radio refractive index and wave propagation conditions in the atmosphere of the Hanoi area. The content of this article uses the data of radio occultation in 2014-2016 and the radiosonde data in 2016-2018, showing that the radio refractive index tends to decrease with altitude, the maximum average value of radio refractivity is 370 N-units, the largest radio refractivity difference between years is not more than 11 N-units, at high altitudes the radio refractivity value is close to the value at standard model of the ITU-R while at a small altitude the difference between the model value and the observed value is up to 60 N-units, the vertical gradient of refractivity and the effective earth radius coefficient is independent with altitude. Based on radio refractivity, it is possible to determine tropospheric delay, which is input data for problems such as satellite positioning, altimetry satellite and under-the-horizon radar
Nghiên cứu sự thay đổi tổ chức tế vi của hợp kim nhôm ADC12 trong quá trình đúc lưu biến
Get PDFTrong nghiên cứu này, nhiệt độ rót và tốc độ làm nguội là hai thông số công nghệ ảnh hưởng trực tiếp đến sự thay đổi tổ chức tế vi của hợp kim nhôm ADC12 đã được nghiên cứu. Kết quả nghiên cứu chỉ ra rằng tổ chức tế vi hợp kim nhôm ADC12 trong quá trình đúc lưu biến thay đổi từ tổ chức tế vi dạng nhánh cây sang tổ chức tế vi dạng cầu với tỉ phần hạt α-Al trên 80%. Tốc độ làm nguội là thông số chính ảnh hưởng trực tiếp đến sự hình thành tổ chức dạng cầu của hạt α-Al. Nhiệt độ rót ảnh hưởng đến kích thước và độ cầu của hạt α-Al. Kết quả nghiên cứu có thể áp dụng để thay đổi tổ chức tế vi của hợp kim nhôm ADC12 giúp hợp kim tăng giới hạn bền và độ giãn dài tương đối, nhưng vẫn duy trì các đặc tính cơ học khác. Nói cách khác, làm tăng độ tin cậy của chi tiết được tạo hình nhờ phương pháp đúc lưu biến
IMPROVING PREDICTION QUALITY WITH XGBOOST MODEL FOR BENDING CAPACITY OF X65 DEFECTED PIPE
Get PDFThere is a desire of a quality model predicting bending capacity of the defected pipe for pipeline integrity assessment. While the analytical model faces with the difficulty in modeling the local defect and corresponding local stress, the Finite Element method is a valuable alternative. A common approach for predicting interested variable is to scrape the result data and develop a data-driven model such as the classical linear regression, CART or XGBoost. Along with generating numerical database with FEM, this study illustrates the advance of XGBoost model compared with its counterparts in predicting the moment capacity of the defected X65 pipe
NGHIÊN CỨU SỰ THAY ĐỔI CHIỀU DÀY THÀNH CHI TIẾT CÔN KHI DẬP TẠO HÌNH BẰNG PHƯƠNG PHÁP THỦY CƠ
Get PDFTrong công nghệ dập thủy cơ, áp lực ép biên và chiều dày tương đối của phôi có vai trò hết sức quan trọng đến quá trình tạo hình. Bài báo sử dụng phương pháp mô phỏng số để nghiên cứu ảnh hưởng của áp lực ép biên và chiều dày tương đối của phôi đến sự phân bố chiều dày thành chi tiết côn khi dập thủy cơ. Dựa trên các kết quả mô phỏng, các tác giả đã tiến hành dập thử nghiệm và cho kết quả nghiên cứu đảm bảo tin cậy