Journal of Military Science and Technology
Tạp chí của Viện Khoa học và Công nghệ quân sự https://online.jmst.info/index.php/jmst
Academy of Military Science and Technology
Thermoluminescent properties of CaF2 co-doped Er3+, Li+ ions
CaF2 nanomaterial co-doped Er3+ and Li+ were synthesized by precipitation method. The structure, morphology and composition of the materials were investigated through X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The thermoluminescent properties of materials have been studied; The results show that the concentration of Li+ ions has an effect on the thermoluminescence intensity of the material. The kinetic parameters of the traps corresponding to the main peak were determined using TLAnal program for analysis of experimental data.
Copyright (c) 2023 Journal of Military Science and Technology
Image restoration for microscopy with wavefront coding technique by Winner filter
Wavefront coding is a powerful technique to extend the depth of field in incoherent imaging systems. However, the quality of images captured by the camera is low, so digital processing is used to restore sharp images. In this paper, we present digital processing for wavefront coding technique in optical microscopy by Winner filter. The experimental model is built. The experimental images are shown. The restored images of the wavefront coding technique are near to the diffraction-limited image of traditional microscopy.
Path following calibration for four-wheel-drive/four-wheel-steer mobile robot (4WD4WS) by referrence objects
In this paper, a method of applying the virtual target targeting algorithm to control the four-wheel-drive/four-wheel-steer mobile robot (4WD4WS) to follow the trajectory, based on information about the actual position of the robot by reference objects along the trajectory is presented. The kinematics of the four-wheel-drive/four-wheel-steer mobile robot was also studied in detail, ensuring the system's stability when operating with speed and direction constraints for each wheel. The process of synthesizing control laws is strictly mathematically guaranteed. The simulation in Matlab shows the research results visually.
Investigating the effects of various input beam profiles on the propagations of light in two-dimensional interfaced binary
In this work, we numerically study how various input beam profiles influence the linear and nonlinear light propagation at the interface of two-dimensional (2D) binary waveguide arrays. It is revealed that, due to the presence of the central homogeneous interfaced waveguides, light beams are effectively steered into the preferred direction. Interestingly, the formation of discretely localized states in nonlinear modes can be intentionally utilized to optimize the stability and intensity of the signals at the central interfaced channels. This study thus opens alternative possibilities to achieve reliable distant beam propagation through discrete optical systems.
Research of the strains of the specialized tube when calculating the simultaneous effects of dynamic pressure and non-stop thermal loads
The article presents a computational model and solves the problem of analyzing the stress state of the specialized tubes when calculating the simultaneous effects of dynamic pressure and non-stop thermal loads. This model of the tube is suitable for surveying the operation of the cannon barrels when firing in automatic firing mode. The results of the internal ballistics task and the heat transfer problem in the tube wall are input parameters for the computational model. The survey is based on the finite element method and is performed by Ansys Workbench software. The survey results obtained are the stresses and strains of specialized tubes when considering static pressure, dynamic pressure, non-stop temperature load and simultaneous pressure and temperature load. This is the basis for evaluating the influence of pressure and temperature factors on the durability of specialized pipes, especially when evaluating the muzzle of the cannon and making recommendations in the process of calculation, design and use of weapons in practice.
Green synthesis of bimetallic nanoparticles from green tea leaf extract
Zero-valent iron could effectively treat many different types of pollutants in the environment, such as chlorine organic compounds, heavy metals and some other inorganic substances. The combination of a metal catalyst with iron was increased the efficiency of pollutant removal, especially persistent organic compounds (POPs). Sustainable, environmentally friendly nanosynthetic methods were gaining more and more attention. In this sutdy, a method using non-toxic chemicals, environment-friendly solvents, simple process was decribes. Bimetallic nano materials Fe/Ni, Cu/Ni were synthesied by using green tea leaf extract in water solvent. In which, the mass of metal nanoparticles was formed the most at the second iron/metal salt molar ratio of 3:1. The optimal conditions for the synthesis of materials were: 12h time, 50 oC temperature, neutral pH.
Effect of additives on fire protection performance of epoxy-based intumescent retardant coating for steel application
In this paper, we will investigate the influence of Al(OH)3 and nanoclay on the fire performance of epoxy-based intumescent retardant coatings. The fire protection properties of the intumescent retardant coatings were characterized by a scanning electric microscope (SEM), Energy dispersive X-ray spectroscopy (EDS), Fourier transformation infrared spectroscopy (FTIR), and Thermal gravimetric analysis (TGA). The results showed that, the sample added 5% Al(OH)3 decreased the plate’s backside temperature of 98-degree celsius compared to the control sample. Besides, char expansion and char residue of the sample added Al(OH)3 have values of 21 times and 17.42% respectively while these values of the control sample have 10 times and 12.61%. Therefore, Al(OH)3 is the most suitable candidate for improving the fire performance of the epoxy-based intumescent retardant coating for steel application in case of fire.
Research and design solar cell systems for electric car charging stations and parking lots
The current global energy crisis has caused many serious consequences. The increasing cost of gasoline and oil has forced governments to pay special attention to this sector. Recently, the price of gasoline and oil in Vietnam has increased to a record of more than 30,000 VND/liter, forcing people to change their needs and habits of using their means of transportation. With reasonable operating costs, the market penetration of electric cars (EC) can be seen as a promising alternative to vehicles with gasoline and diesel engines in order to reduce environmental pollution as well as operating costs. In this study, we designed and calculated the capacity for a solar charging station to charge electric cars (VFe34 of Vinfast) and electric bicycles for household use with a capacity of P = 9 kWp, capital = 179.672.000 VND. The payback period of the model is 5,2 years, and the estimated profit is 34.197.878 VND/year. With solar charging stations for 12 electric cars having an additional investment for independent solar charging station models, grid-tied solar charging stations with storage and without storage show that the efficiency is the profit of each model. The cost of materials is 759.176.000 VND for a grid-tied solar charging station, the payback is 4,1 years (from the third year onwards, more than 180 million VND per year). Instead of designing a conventional car charging station, this study has presented models of smart charging stations with integrated solar cells to demonstrate high efficiency and practical applications
TPC decoder design for FPGA implementation
In this paper, the FPGA implementation of Turbo Product Code is presented. The design is based on the iterative decoding structure with using Chase-Pydiah algorithm for better decoding performance. In pacticular, circuit design and implementation based on the simplified algorithm without using multiplication. Simulation and implementation result show that, the decoding perfomance of this presented algorithm is not reduced. The 800Mbps TPC deccoder was achieved for FPGA implementation on the Xilinx Artix7 xc7a200tfbg484-1 platform at the 200MHz system clock.
Research and building kinematic model for transverse system of the motion platform on specialized vehicles
Stabilization system on specialized vehicles allows the motion platform type pan-tilt system to be stabilized in horizontal and vertical planes while the vehicle is on moving. Therein, the transverse system is an electric-drive one using a separated excitor DC motor and the power element is an electromagnetic amplifier. In this paper, the research results in order to build a kinematic model for the system based on the physical relationships and experimental results are presented. Then, an algorithm control is proposed to improve the quality of platform stabilization in the horizontal plane. These results are simulated to prove the correctness of the model and the effectiveness of the proposed algorithm.
Embedded computer deployment solution using Linux operating system on ZYNQ
In this paper, some research results on deploying an embedded computer using Linux operating system on Xilinx's ZYNQ hardware platform are presented. ICs of the Zyqn family released in the last 10 years have been reshaping popular embedded computing platforms, with flexible synergies between ARM and FPGA family of processors that deliver high efficiency first. In this paper, a high-speed GPIO design is implemented, in which the hardware on the FPGA, the driver on the Linux operating system, and the control software are jointly implemented. The test results have demonstrated the ability of the GPIO port to operate at high speed and flexibility when controlled via software on the Linux operating system.
Structures of phenolic compounds isolated from Eupatorium adenophorum
Nowadays, phytochemical profiles of plants are the basis for the evaluation of their biological activities and ecological impact on environment and other living species. Chromatographic separation and NMR structural analysis were used in this paper to study the occurrence of six phenolic compounds in water fraction from the leaves of Eupatorium adenophorum Spreng. Structures of the compounds were identified as 4-hydroxybenzoic acid, methyl 3,4-dihydroxybenzoate, isovanillic acid, 5-O-glucopyranosylthymoquinol, 2-O-b-D-glucopyranosylcinnamic acid, and quercetagetin 7-O-b-D-glucopyranoside.
Influence of fabrication method of copper shaped charge liners on the penetration depth into steel targets
This paper presents the penetration behavior of copper shaped charge liners produced by four different techniques, including deep drawing, deep drawing followed by metal spinning, SPS sintering and SPS sintering followed by metal spinning technique. The results show that the grain size of copper liners has a strong effect on the penetration depth into steel targets. The metal spinning step led to the appearance of the subgrains and the increase of dislocation density and hence, improved the penetration depth of the copper shaped charge liner. Accordingly, the penetration depth of the shaped charge liners produced by deep drawing followed by metal spinning and SPS sintering followed by metal spinning into steel targets reached the highest values, which are about 80 mm. Meanwhile, the penetration depth of the shaped charge using SPS sintered liner is 70.5 mm. The copper liner made by deep drawing produced an unstable depth and was about 50 mm. This work also shows the formation of the subgrains with a width in the range of 300 to 500 nm and a length from 1 to 3 mm in the liners microstructure after metal spinning.
Investigation and design of drift buoy system applied in ocean environment data collection
Drifting buoys are widely used in the world to measure oceanographic and environmental parameters. Key science and technology program at ministerial level of Natural Resources and Environment: “Research, innovation, design and manufacture of specialized equipment for a basic investigation of natural resources and environment, and waste treatment in the period 2021-2025” has built the Project of research, design and manufacture drift buoys to collect marine data, Code: TNMT.202103.02. The content of this paper is part of the projective research results to describe case studies on solutions to calculate, design and manufacture drift buoys suitable to Vietnamese conditions on the basis of comparing technical specifications with commercial drifting buoy systems in the world.
The influence of some factors on the characteristics of metallized incendiary mixtures
In this article, the influence of some factors on the characteristics of metallized incendiary mixtures (pyrogels) was studied. The pyrogel-type contains benzene, polyisobutylene, magnesium, aluminum-magnesium alloy, sodium nitrate, and different additives. It is shown that the molecular weight of polyisobutylene, the amount of aluminum-magnesium alloy, the particle size of metal combustibles, and the amount and type of polyester threads have different effects on the heat of combustion, flash point, burning rate, flame height, and adhesion to the material surface. The optimal pyrogel contains 38-40% thickened benzene - PIB with molecular weight 175000-225000, 25-27% aluminum-magnesium alloy with particle size ≤ 160µm, 10-12% magnesium powder with particle size ≤ 180µm, 15% sodium nitrate, 8% phenol-formaldehyde resin and 1.5% (over 100%) 3D polyester threads.
Time series prediction based on machine learning: A case study, temperature forecasting in Vietnam
In recent years, there has been a surge in interest in the subject of machine learning for prediction. In this study, a temperature dataset of Vietnam’s stations is examined in order to anticipate temperature. Several forecasting models are used to accomplish this goal. First, a traditional time-series forecasting approach such as Seasonal Autoregressive Integrated Moving Average is used (SARIMA). Then, more complex approaches such as XGBoost, Encoder-Decoder, and Prophet are used. The models' performances are compared using several accuracy assessment methods (e.g., Root Mean Squared Error (RMSE) and Mean Absolute Error (MAE)). The findings demonstrate the superiority of the deep learning approach over the other methods.
Recent advances in synthesis of noble metal and non-noble metal catalytic materials for hydrogen evolution reaction
Since the 20th century, the world has been challenged by the rapid exhaustion of fossil energy resources and their global influence on climate change, and environmental pollution. In this regard, hydrogen has been considered as an endless and green source of energy to replace fossil fuels, playing a vital role in the hydro economy of the 21st century onwards. Numerous catalytic materials have been studied and developed to accelerate the hydrogen evolution reaction rate and efficiency. Considerable efforts have been paid to look for strong, stable, and economical electrochemical catalysts for hydrogen production and fuel cells. In this report, we review recent advances in the synthesis of non-noble metal catalytic materials.
Investigating injector angles to eliminate spray-wall impingement in a manifold port injection system of gasoline engines
There has been an outstanding improvement in injection technology in the spark ignition (SI) engines’ fuel supply systems, from traditional carburettors with throttle body injection (TBI), manifold port or multi-point injection (MPI) to direct injection (DI). This paper has developed an MPI intake manifold model and investigated fuel injector angles using a multiphase CFD package provided by FloEFD software. A wide range of injector angles from 22 to 30 degrees has been investigated in order to evaluate the influence of the injector angle on the wall-wetting issue, a critical problem of manifold injection systems in SI engines. The intake air pressure differential in the manifold was also evaluated. The results show that the fuel injector angle affects the multiphase flow in the MPI system. The manifold diameter meets the design specifications, and the pressure differential in the manifold is quite small. With an injector angle of 25 degrees, the wall-wetting issue is minimal. This model could be used for further studies on engine performance and emission formation.
Building a baseband signal processing algorithm for unmanned aerial vehicle detection radar
In this paper, the construction of a baseband signal processing algorithm for unmanned aerial vehicle (UAV) detection radar by using continuous linear frequency modulation (FMCW) signal is presented. On the basis of the built algorithm, the article presents the contents of simulation research in Matlab environment, and conducts experimental research by designing and deploying signal processors on the technology platform FPGA. The results of the study show that FMCW radar can be used to distinguish UAV targets from normal targets by the micro Dopple signature. The signal processor is the basis for building a complete UAV detection radar in the future.
Study on the effect of efficiency recovery ammonium and phosphate in rubber wastewater by struvite precipitation
The removal and recovery of Ammonium and phosphorus from rubber wastewater is an important issue to reduce water and environmental pollution. The aim of this study was to recover N and P from rubber wastewater through a crystallization process at different operational conditions. The effects of pH, Mg/P/NH4 molar ratio, and reaction time on the yield of struvite recovery were discussed. The results showed that at the pH value of 9.5, The reaction time is 60 minutes, the optimal mole ratio Mg2+: P-PO43-: N-NH4 is 1.3: 1: 1, the efficiency of ammonium and phosphorus removal is 82 and 96%, respectively; The volume of struvite precipitate obtained is 4.16 g/liter of rubber wastewater.
Developing the method calculation dynamics for the design electromagnetic relay steering machine of a guided flying machine type 9M111
In this paper, the method of calculation dynamics for design in the form of an electromagnetic steering machine of flying machine type 9M111 is presented. On the basis of determining the external force acting on the rudder of the aircraft, structural-electromagnetic parameters for steering motion, establishing and solving a system of differential equations of motion, and calculation dynamics of steering machine, as a basis for determining the design parameter domain of the model steering machine through surveying the influence of structural-electromagnetic parameters on the steering response delay. The mathematical model can be applied to calculate the design of an electromagnetic relay steering machine for some similar flying machines.
A designing solution for the C-band digital phase shifter
Nowadays, phase shifters are widely applied in modern radar and electronic warfare systems. The design of phase shifters is becoming more and more compact, with large phase coverage, high max input power, and high efficiency at a lower cost. This paper presents technical solutions and technology used in designing of C-band phase shifter. The phase shifter uses multiple PIN diodes in combination with the stripline in order to reduce the overall size while ensuring the accuracy of the phase shift step according to design requirements.
Geometries, stability and dissociation behavior of AgnCo clusters (n = 1-12): A theoretical investigation
The geometric structure, stability, dissociation channel and magnetism of AgnCo clusters (n = 1–12) have been studied using density functional theory. The results show that the Co atom tends to choose the highest coordination position. The ground state of AgnCo clusters prefers the planar motif at small sizes (n less than 4) but favors 3D structures at larger sizes (n = 5–12). The stability of clusters is not only governed by the symmetric geometry but also strongly depends on the electronic structure and the filling rule of the electron shells. The Ag9Co cluster with 18 valence electrons fully filled the electronic shell (1S21P63dCo10), which is considered as a potential superatom. The total magnetic moment of AgnCo clusters is governed by the electron localization on the Co atom. The relative stability of the clusters is determined by the average binding energy, the second-order difference energies, and the dissociation energies.
Study to select binders to synthesize zeolite X for the drying block of air compressor
This paper presents the research results on the selection of binders for preparing rod-shaped X zeolite used in drying blocks to remove condensate from the air compressor system. The hardness and adsorption capacity of zeolite particles synthesized using 3 different binding agents, including silica sol, boehmite, and carboxymethyl cellulose, which were compared to select the appropriate agent. The results showed that zeolite particles made from boehmite binder with 12% content by weight had good hardness, ion exchange capacity and adsorption capacity for water and toluene, which are 105 meq/100g, 11,25g/100g, and 11.17 g/100 g, respectively.
Evaluate the potential of integrating hydrogen fuel cells into the Bach Long Vy Microgrid
Microgrid develops rapidly in the world as well as in Vietnam recently. Microgrid has the advantage of being able to integrate renewable energy sources, environmentally friendly, and especially suitable in remote island areas where the option of supplying electricity from the mainland is not feasible. However, the planning and operation of the microgrid to optimize production costs is a challenging task. In this paper, the microgrid of Bach Long Vy island district is used as the research model. Three power supply scenarios for Bach Long Vy island district's power grid are compared and evaluated. Homer software is used to evaluate the economic factors of proposed scenarios. The evaluation results show that the option of integrating hydrogen storage into the current system on the island is the optimal option in terms of production costs. In addition, this option also reduces emissions from diesel generators.
The algorithm for determining the switch rule of continuous steering on two-channel flying objects with the requirements of normal acceleration
The article deals with a solution to build an algorithm for determining the switch rule of continuous steering pairs on the two-channel flying objects with the requirement of normal acceleration while approaching the maneuvering air target. The content of this paper focuses on determining the dependence of the attack angle and the edge sliding angle on the steering deflection angle. Thereby, the authors have built the dependent expression of the steering deflection angle on the desired normal acceleration. Through the analysis of a mathematical model describing the flight kinematics of flying objects, the authors have determined the switching rule of continuous steering pairs is a harmonic function. Where frequency is the rotation speed of the longitudinal axis, amplitude and phase as a function of the flying object’s characteristics and the desired normal acceleration.
Solution for design and manufacture of standard frequency generator block 1-OC.VN for P-845 radio station
This paper presents study results on application of existing technology to design and manufacture the standard frequency generator block 1-OC.VN for P-845 radio station with requirements of wide frequency band, small frequency steps, fast response time and the suitability for both technical and tactical features.
Research and design the taper angle of a single use piston
In this paper, using numerical simulation combined with experiment, the most suitable design for piston taper angle in the single use piston of the piston - cylinder system has been proposed. The research process shows that, when the piston has a taper angle of 12o for the design of the cylinder tail taper angle of 20o, the resulting deformation, the equivalent stress of the cylinder tail is the smallest as well as the deceleration time of the piston is the greatest, thereby increasing the tightness and minimizing the impact of the piston-cylinder collision on the sealing process and the operational reliability of the system. The results after the study are proven experimentally, the experimental results show that the simulation results are reliable and highly applicable. The results of the article are applied to manufacturing and testing 82 mm silent mortar systems.
Improving the image quality of optical systems with radially symmetrical phase mask
An optical system with a radially symmetrical phase mask allows to extend the depth of field. However, the contrast of the optical system is still lower than that of the diffraction pattern of the traditional optical system. In this paper, we introduce a new method for image enhancement of optical systems with radially symmetric phase masks. The optical system with a traditional radial symmetric phase mask would result in a dot point spread function. The optical system with an improved symmetric phase mask results in a dark center point spread function. The two images that will be obtained correspond to the optical system with two phase masks. On the basis of these two images, a mathematical relationship is proposed in order to obtain good quality images. The simulation results have demonstrated the proposed method to improve the image quality of the optical system with the radial symmetrical phase mask.
Researching solutions for production of electrical parameter testing module on battle control vehicles
This paper presents a method of manufacturing a module to test and monitor electrical parameters on the basis of integrated electronic circuits to process peripheral signals to ensure inspection and supervision. Using the module makes the system compact, improves accuracy and reliability during calibration and calibration, and uses test equipment to monitor electrical parameters on combat control vehicles.