Journal of Science and Technique
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STUDY OF INFLUENCE OF COLD ROLLING AND ANNEALING ON ULTIMATE TENSILE STRENGTH OF AA2024 ALLOY USING BOX-BEHNKEN EXPERIMENTAL DESIGN
Get PDFThis study investigates the effects of thermo-mechanical processing parameters, specifically cold rolling and annealing, on the ultimate tensile strength (UTS) of AA2024 alloy, employing a Box-Behnken experimental design. The deformation during cold rolling, the annealing temperature, and the time annealing were varied to evaluate their individual and combined effects on the UTS. The results demonstrated that the UTS increased with deformation from 50% to 60%, but decreased with higher annealing temperatures (460°C - 500°C) and extended annealing times (10 to 30 minutes. Among the parameters, annealing time exhibited the most significant influence on UTS, followed by deformation level and annealing temperature. The optimized parameters - 60% deformation, 460°C annealing temperature, and 10 minutes time annealing - predicted a UTS of 628 MPa, with experimental verification confirming a 3% deviation. This research underscores the critical importance of controlling thermo-mechanical parameters to optimize the mechanical properties of AA2024 alloy, offering valuable insights for industrial applications
FORMULATION AND SEVERAL CHARACTERISTICS OF THE SMOKE COMPOSITIONS BASED ON RED PHOSPHORUS
Get PDFRed phosphorus is an important ingredient in the manufacture of pyrotechnic smoke and is likely to be in service for many years. One of the most effective ways to use smoke screens is to protect special vehicles from laser and infrared guidance systems. In this work, the formulation, obscurant and emission characteristics of the smoke composition in smoke devices used in special vehicles were determined and evaluated. Research results show that the smoke composition comprises red phosphorus, sodium nitrate, Al-Mg alloy, and fluorine-containing polymers. The outcomes also demonstrated that the smoke screen has a high attenuation capability to 1.064 µm laser radiation and strong infrared emission in both wavelength ranges of 3 - 5 µm and 8 - 14 µm
DETERMINATION OF 4-METHYLIMIDAZOLE AND 2-ACETYL-4-TETRAHYDROXY-BUTYLIMIDAZOLE IN CARAMEL COLOR AND PRODUCTS BY LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY
Get PDFThe simultaneous determination of 4-MEI and THI in caramel and products by LC-MS/MS was developed with several advantages of simplicity, selectivity, and high sensitivity. Chromatographic separation was performed using a C18 column (100 × 2.1 mm, 1.7 μm), with a mobile phase consisting of ammonium formate pH = 4 and acetonitrile containing 0.1% formic acid employing a gradient elution mode. The analytes were detected using an MS/MS double mass spectrometer with an ESI+ ionization source. Samples were cleaned and enriched on a SPE MCX column. Method validaion resulted in a linear range of 5.0 - 500 ppb for 4-MEI, and 1.0 - 500 for THI, with LODs of 0.30 g/kg for THI and 1.5 μg/kg for 4-MEI, and LOQs of 1 μg/kg for THI and 5 μg/kg for 4-MEI. Repeatability and reproducibility for 4-MEI ranged from 2.9% to 9.1% and 2.9% to 11.8%, respectively, and for THI from 3.5% to 9.4% and 4.8% to 11.5%, respectively. Recovery rates for with 4-MEI and THI met AOAC's requirements, ranging from 82.7% to 106.4% and 87.2% to 109.7%, respectively. Application of the analytical method for 24 market products, including caramel, beverages, condiments, and cakes, showed that the 4-MEI and THI concentrations in consumer products were within the permissible limits, while pure caramel samples exceeded the permissible limits for THI concentrations
RESEARCH THE INFLUENCE OF STIFFNESS OF BEAM ON THE FORCE TRANSMISSION TO THE PONTOON AND ON THE MOMENT IN THE BEAM DUE TO CONCENTRATED LOAD FOR PONTOON-SERAPATE FLOATING BRIDGE
Get PDFThe pontoon-separate floating bridges have many advantages to apply to the construction of civil floating bridges in Vietnam. This article presents the study of the influence of beam stiffness on the force transmission of concentrated load to the pontoon and the bending moment in the beam caused by this load, as a basis for designing civil poonton bridge to carry loads for small tonnage motor vehicles serving rural traffic. The author uses theoretical research methods using SAP2000 software. The results show that the moment in the beam is directly proportional to the stiffness of the beam. The transmission of force to pontoon away from the force application point is also directly proportional to the stiffness of the beam. Initially, the force transmitted to the pontoon near the force application point is inversely proportional to the beam stiffness, and then directly proportional to the beam stiffness
STUDY ON THE TROPICAL-STORM-GENERATED WAVE FIELD ON THE SEA AREA AROUND LY SON ISLAND
Get PDFLy Son is a frontline island of our country that is often affected by adverse weather conditions such as monsoons or tropical storms. Studying the hydraulic parameters of tropical storms, including the storm's wave field, to determine extreme conditions plays an important role in forecasting, planning and construction of hydraulic works. The author uses the two-dimensional wave propagation model MIKE 21 SW to simulate the wave field of Molave storm 2020 in Ly Son sea. The results show a good agreement between the values obtained from the model and the actual measurements at Ly Son station. Based on the results obtained, the author proposes a method to simulate storm wave fields that is relatively accurate and effective. In particular, current standards based on wind speed and wind fetch still have many limitations. This is valuable in the actual design and planning of hydraulic works
FUNCTIONAL INTEGRAL APPROACH AND THE EIKONAL APPROXIMATION TO THE POLARON ENERGY AND MASS
Get PDFThis article uses the functional integral method and eikonal approximation to calculate the first-order correction for the energy and (effective) mass of the Polaron. The obtained results have demonstrated the effectiveness of the functional integral method compared to conventional perturbation theory when considering the Polaron problem in solid crystal
FABRICATION AND ELECTROCHEMICAL CHARACTERIZATION OF CATHODE MATERIAL Na1.0Li0.05Mn0.6Ni0.3Al0.05O2 FOR SODIUM ION BATTERIES
Get PDFSodium-ion batteries exhibit structural and operational similarities to lithium-ion batteries, and they are increasingly recognized as a viable alternative to lithium-ion batteries. In this context, it is imperative to investigate electrode materials specific to sodium-ion batteries to enhance their capacity, stability, and cost-effectiveness, thereby facilitating their commercialization in the near future. In pursuit of these objectives, this study successfully synthesized Na1.0Li0.05Mn0.6Ni0.3Al0.05O2using a sol-gel method followed by calcination. The resulting material demonstrated a P2 crystal structure and achieved a maximum specific capacity of 142.2 mAh g-1 at a discharge current density of 10 mA g-1 within the voltage range of 1.5 to 4.1 V. Furthermore, the material exhibited commendable stability, maintaining 89.1% capacity retention after 50 cycles and 76.4% after 100 charge-discharge cycles at a current density of 15 mA g-1 within the same voltage range, indicating its potential as an cathode material for sodium-ion batteries
SOLUTION SELECTION FOR FASTER ESSENTIAL MATRIX BASED STEREO VISUAL ODOMETRY
Get PDFFor autonomous navigation systems used in robots and self-driving vehicles, the usage of sequence images captured from single or multiple cameras for localization has been widely adopted due to both the low cost and high accuracy. The approach using essential matrix estimation for calculating the transformation is so popular that the essential matrix is estimated from five points which is the minimum number of points for pose estimation. However, each five pairs of points provides up to ten solutions for the essential matrix. In this paper, we propose an approach to improve the computation speed of the essential matrix by selecting the number of solutions based on a comparison with the previous essential vector of the two consecutive frames. The proposed method evaluated on the KITTI dataset shows at least 15% reduction in computation speed compared to the conventional method
DIRECTION OF ARRIVAL ESTIMATION BASED ON SMOOTH MUSIC ALGORITHM COMBINED SPECTRUM SELECTION TECHNIQUES OF NOISE CHARACTERISTICS OF MARINE TARGETS EQUIPPED PROPELLER
Get PDFThis article demonstrates a proposal for a direction of arrival (DOA) estimation algorithm for passive sonar systems based on the combination of the smooth multiple signal classification (Smooth MUSIC) algorithm and frequency bin selection (BS) of the sound of marine propeller-equipped targets, so-called BS-SMUSIC. The harmonics of propeller shaft and blade frequencies are considered useful information for detecting targets and estimating their parameters, including DOA. Low frequency analysis recording (LOFAR) is utilized to implement BS. By analyzing MUSIC-based algorithm together BS, passive DOA estimation algorithms have been significantly improved. Simulation results have been given in both cases: uncorrelated and correlated sources. Outcomes demonstrate that the BS-SMUSIC algorithm has the best performance in comparison to three MUSIC-based algorithms (MUSSIC, Modified MUSIC and Root MUSIC) in all investigation cases: narrow band signals at 5 dB of signal to noise (SNR); wideband signals at -5 dB of SNR. Besides, BS-SMUSIC algorithm also archives the lowest root mean square error (RMSE) in SNR range -5 dB to 20 dB. In the SNR range, the RMSE of BS-SMUSIC algorithm remains stable and is about 0.3 ◦ at -5 dB of SNR. This performance reflects its ability to ensure stable operation, super resolution and high accuracy of BS-SMUSIC algorithm for the passive sonar systems
EXPERIMENTAL STUDY ON THE APPLICATION OF TRC TO ENHANCE THE LOAD-BEARING CAPACITY OF REINFORCED CONCRETE SLABS
Get PDFTo enhance load-bearing capacity and prevent structural damage, reinforced concrete elements are often strengthened with additional layers of material. This study investigates the bonding performance between Textile Reinforced Concrete (TRC) and reinforced concrete slabs through four-point bending tests. The primary objective is to assess the effectiveness of surface grooving on the old concrete to improve the adhesion between the TRC layer and the slab. Experimental results demonstrate that TRC strengthening significantly improves both the load capacity and mid-span deflection of the slabs. Specifically, TRC-strengthened reinforced slabs exhibited an average 137% increase in load-bearing capacity and a 53% increase in mid-span deflection compared to unreinforced slabs. Notably, no debonding occurred, even at failure, confirming the reliability of the grooving technique in ensuring a strong bond. The study also concludes that TRC is an effective method for enhancing the flexural strength of reinforced concrete slabs, while also improving safety under high loading conditions