Journal of Military Science and Technology

Advances in manufacturing multi-layer materials for thermal camouflage applications

2024-02-27T03:36:29+00:00

Thermal imaging reconnaissance technology has been widely and effectively exploited in the military sector to serve reconnaissance, search and track objects and other purposes, because the heat signature of any target is very difficult to conceal, and easily be detected by thermal imaging reconnaissance devices. Thermal imaging camouflage covers are researched and developed to limit detection by thermal imaging devices by minimizing the heat signature of the target. Multi-layered Textile Structures (MTS) coverings are proposed basing on overlapping layers of different materials, combining and optimizing the properties of individual materials to create one with thermal camouflage properties. This article studied and summarized national and international research on thermal imaging camouflage coverings with multi-layer structures, as a basis for orienting research, developing a design method, optimizing and manufacturing a covering with a multi-layer structure that effectively thermal camouflages by domestic resources.

A solution for pulse measurement based on the time-to-digital principle using FPGA

2024-08-26T04:17:46+00:00

The process of repairing and maintaining digital signal processing modules always requires specialized measuring equipment, which takes a long and tedious time. In order to reduce the time and cost of technical maintenance and repair, the authors proposed a design solution for pulse parameter measurement based on FPGA technology based on the time-to-digital converter principle. Currently, these pulse parameter meters are being applied in the 394ПП04-KT, module testing and analysis device.

Building a satellite navigation receiver on FPGA technology combined with ARM to serve special applications

2024-08-26T04:14:09+00:00

This paper proposes a solution to build a satellite navigation receiver based on FPGA technology combined with ARM. The proposed solution is based on classic methods and algorithms combined with a number of self-developed auxiliary algorithms implemented on self-designed and manufactured hardware. Signals from satellites are received by the frontend chip, then processed and given positioning results by the backend block, which is implemented by self-designed and manufactured hardware with the core of the Zynq chip. In doing so, satellite navigation receivers have a lot of flexibility and, most importantly, overcome some of the limitations that manufacturers of commercial positioning receiver chips have locked. In addition, the research results are also a premise for designing and manufacturing satellite positioning receiver chips for special applications as well as for Vietnam's own satellite positioning system in the future.

Optimization of compressive technology on the composition pyrotechnic based on Magnesium-Teflon-Viton with nano additives by Box-Behnken method

2024-05-07T02:41:28+00:00

Nowadays, infrared decoy flares are one of the effective means used to protect aircraft against infrared guided missiles. In the infrared decoy projectile, the composition pyrotechnic based on Magnesium-Teflon-Viton (MTV) is granulated and compressed, or extruded into cylindrical pellets of various sizes. This article presents research on optimization of MTV pellets compression technology parameters including sample weight (g), compression pressure (tons) and compression holding time (s). The applied Box-Behnken experimental planning method has resulted in optimal density of 1.68 g/cm³ and compressive strength of 20.5 MPa (sample mass of 3.6 g, compression pressure of 1 ton and time pressure holding time 40 s).

Studying the resistance to fluorescent UV-condensation exposures of nano coating on natural rubber

2024-08-26T04:14:27+00:00

Rubber materials are often destroyed and reduced durability by the impact of environmental factors such as: ozone, oxygen, heat, UV rays.... This article has researched the anti-aging ability of nano coatings DDN-01 for natural rubber under fluorescent uv-condensation exposures. With the protection of the coating, after 20 radiation-heat-humidity acceleration cycles, the tensile strength of rubber remains higher than 84% and maintains a stable surface structure. This research opens up broad application possibilities of nano solutions to protecting and improving the durability of rubber and non-metallic materials.

Optimization of 4-chlorophenol decomposition by H2O2 activate catalytic magnetic iron oxide an activated carbon carrier

2024-08-26T04:15:03+00:00

Wastewater from chemical plants that produce pesticides always carries a large amount of organic matter that is difficult to decompose. One of them is the compound 4-chlorophenol, which has difficult-to-decompose properties, is durable in the environment, and is also listed in the group of substances that are likely to cause cancer in humans. In this study, the 4-chlorophenol compound was treated with heterogeneous Fenton by H₂O₂ activated by magnetic iron oxide nanoparticles on activated carbon. Magnetic iron oxide nanoparticles were successfully synthesized and mounted on activated carbon 10-15 nm in size with material surface morphological parameters such as specific surface area 330.28 cm²/g; total pore volume 0.16 cm³/g; magnetization 8.19 emu/g. The optimization of the 4-chlorophenols decomposition reaction with pH parameters, the content of catalytic materials, and the initial concentration of 4-chlorophenol is carried out using the Box-Behnken Design. The results showed that the removal efficiency of 4-chlorophenol was 96.5% achieved with optimum parameters pH 2.9; catalytic concentration 0.32 g/L; initial concentration of 4-chlorophenol 92.3 mg/L. The results of the study show the efficiency of the decomposition of an organic compound using magnetic activated carbon.

Fabrication of HgZn3 material and their application as electrodes in mercury oxide-zinc batteries

2024-08-26T04:13:49+00:00

The mercury oxide-zinc battery is a primary electrochemical cell that operates in an alkaline environment. It finds applications in many disciplines such as science, technology, medicine, and field equipment. In order to improve resistance to electrode corrosion in an alkaline environment and to maximize discharge efficiency and battery capacity, it is necessary to amalgamate zinc. This work described a technique for producing HgZn₃ amalgamated zinc. The research findings indicated that a mass ratio of 3:1 between Zn and HgCl₂ is the most favorable for producing the highest quality amalgamated product to be utilized as the negative electrode in a mercury oxide-zinc battery. The material underwent characterization using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and electron microscopy (SEM). The battery depleted to a voltage of 0.9 V during a span of roughly 209 hours, resulting in a capacity of 2823 mAh.

Research on fabrication of modified graphene nanoplalelets conductive ink

2024-07-09T00:47:35+00:00

In this experiment, we studied and successfully modified graphene with oleic acid, proposed the modification process and selected the optimal 2.5% oleic acid content to modify GNPs. From there, we successfully manufactured conductive ink with CAB binder, ethyl acetate solvent and modified nano-graphene. Through the process of surveying and evaluating the effects on the material synthesis process, the optimal parameters for manufacturing conductive ink are given: ink with a composition ratio of 6% graphene powder (modified with 2,5% oleic acid) and 0.75% cellulose acetate butyrate binder dissolved in ethyl acetate solvent. In this ink formula, the lowest resistance obtained is 22 Ω and the resistivity is 7.56 Ω/cm^-2.

Optimal power management for hybrid electrical vehicle

2024-08-26T04:16:15+00:00

This paper introduces an innovative optimal energy management strategy tailored for a hybrid electric-powered hydraulic excavator system. The aim is to bolster power performance, extend the lifespan of power sources, and optimize hydrogen usage. In this system, the fuel cell serves as the primary power source, while integrating supercapacitors and batteries offers benefits such as enhancing power performance and storing regenerative energy for future use. To efficiently distribute power among these three sources and maximize the utilization of regenerative energy, we propose an energy management strategy. This strategy combines fuzzy logic control with a rule-based algorithm. Moreover, we optimize the parameters of the fuzzy logic system using a combination of the backtracking search algorithm and sequential dynamic programming. This optimization aims to reduce hydrogen consumption and prolong the lifespan of the power sources. Simulation results demonstrate that our proposed energy management strategy significantly enhances vehicle performance, improves fuel economy of the hybrid electric-powered hydraulic excavator system, and enhances the durability and efficiency of the battery and supercapacitor systems within the fuel cell system.

Adaptive control with non-recursive schemes for robot systems

2024-05-20T03:20:43+00:00

In this paper, the authors consider the design of adaptive controllers for robot systems with uncertain system parameters. A new non-recursive adaptive controller is proposed for a robot system, with the controller coefficients being time-varying and updated online to avoid the need for an estimator to estimate the uncertain model parameters. The controller is analyzed and shown to be stable in the Lyapunov theory. The tracking error of the joint trajectories and all the parameters in the closed-loop system converge asymptotically to the origin and are bounded. Finally, simulations are performed to verify the feasibility and effectiveness of the proposed control method..

AC drive control design with reinforcement learning techniques

2024-06-04T03:44:23+00:00

Three-phase induction motors (IM) are widely known in industrial applications for their low cost and minimal maintenance. Control of AC induction motors based on Field-Oriented Control (FOC) and vector control with classic PID control laws are reliable techniques commonly used in industry. However, due to the nonlinear nature of electric machines and their susceptibility to external disturbances or parameter variations, conventional controllers often struggle to meet control requirements. Reinforcement Learning (RL) is an online learning technique, model-free, capable of handling parameter variations. These characteristics make reinforcement learning a potential candidate, acting as an adaptive controller that can replace conventional controllers.

This article proposes the design of a control system for three-phase induction motor drives based on reinforcement learning techniques. The proposed controller utilizes a reinforcement learning agent with the DDPG algorithm to replace the PI controllers of the current loop circuit in conventional FOC control. The performance of the controller has been validated under various operating conditions through computer simulations in MATLAB/SIMULINK

Building a MRAC-HIL adaptive control system for DC electric motors

2024-08-26T04:15:39+00:00

This article proposes an approach to build a model reference adaptive control MRAC system for DC electric motor using MRAC-HIL coordination based on the RCP rapid control prototyping tool MicroLabBox. In this plan, the reference model, control algorithms and functional input-output blocks were built based on the MATLAB-Simulink library and additional libraries from dSpace. The entire models and algorithms were compiled, downloaded to the MicroLabBox, run and tested in real time. The experimental results of using the direct Lyapunov method and the speed gradient method confirm the advantages of adaptive control which applied to control objects with variable or uncertain parameters. Control system is stable, the performance is good and depends on reference model only. The idea of coordinating MRAC-HIL can be extended to other control objects, tools, and development platforms.

Synthesis of intelligent control algorithms for a class of naval aerial vehicles

2024-08-26T04:15:57+00:00

Autonomous aerial vehicles in the Navy are modern aircraft widely used in military applications. Current techniques are primarily based on linear control theory, which may overlook nonlinear elements in the model or external disturbances in the operational environment. Therefore, this paper presents a method for synthesizing adaptive fuzzy neural network control algorithms for a class of autonomous aerial vehicles in the Navy to stabilize desired characteristic angles. The study is conducted in a Matlab/Simulink environment with assumed parameters, and comparisons are made with a PID controller to demonstrate the advantages of the proposed algorithm.

Adaptive amplitude and phase deviation compensation for phased-array radar receivers with digital beamforming

2024-08-26T04:17:28+00:00

The article presents a method for compensating for amplitude and phase deviation among channels in phased-array radar receivers with digital beamforming. The digital distorter for amplitude and phase mismatch compensation is designed based on digitized signals to be suitable for practical implementation in FPGA chip. The architecture of the digital distorter performs calculations of nonlinear inverse characteristic among channels. Adaptive algorithms for adjusting the characteristics of the digital distorter are also presented. Simulation results of the distorter design using Matlab software are provided to demonstrate the effectiveness of the proposed method.

Modelisation, Analysis and prevention sub-synchronous resonance phenomenon at Vung Ang thermal plant

2024-08-26T04:16:33+00:00

This paper presents a method for building models, modelisation, analysis and prevention the phenomenon of subsynchronous resonance in the power system, applied to Vung Ang thermal power plant. Through simulation and analysis results, the author proposes solutions for operating the power system, using appropriate vertical compensation capacity, and using passive filters to minimize the risk of sub-synchronous. Calculation results on the power system model viewed from the Vung Ang thermal power plant have been tested, demonstrating the risk of subsynchronous resonance incidents as well as the effectiveness of the filter method in eliminating except this incident.

A method of reducing insertion loss for microstrip filters

2024-01-04T08:11:40+00:00

Based on the theory of multiple coupled-resonator filter, coupling matrix and microstrip square open loop resonator, this paper studies a method of designing bandpass microstrip filter in order to reduce insertion loss. The results of simulation on ADS software and measurement on vector network analysis machine of a sample of designed filter showed that the method can reduce insertion loss which compare to other common microstrip filters. The method can be completely used to design microstrip filters with low insertion loss and high selectivity, applying for wireless systems.

Research on building a model of multi-sensor optoelectronic system to control the surface of large objects

2024-08-26T04:14:45+00:00

This study proposed and studied a completely new optoelectronic system (OES) with multi-sensor matrix structure (CMOS) for measuring the main reflector surface deformation (MR) of a big-sized radio telescope. This system includes 24 multi-sensor cameras, in each 25 sensors are arranged, and each sensor is responsible for image acquisition of a control point on the MR surface. The simulation and calculation studies show that angular and linear errors when determining the initial position of multi-sensor cameras do not exceed 0.05 arcsecond and 0.005 mm, which will ensure an accuracy of 0.1 mm when locating control points on the main reflector surface. At the same time, the simulation also shows that the proposed EOS can control the entire reflector with the surface error not exceeding the limit value of 0.05 mm.

Influence of dispersion properties on pulse propagation in GeSe2-As2Se3-PbSe chalcogenide photonic crystal fibers

2024-03-12T00:45:08+00:00

In this paper, we present the results of a study on pulse propagation in photonic crystal fibers made from GeSe₂-As₂Se₃-PbSe chalcogenide. We employ the Slip-Step-Fourier method to solve the general nonlinear Schrödinger equation, seeking solutions for the output pulse during the propagation in the photonic crystal fiber. The results indicate that the dispersion properties significantly influence the characteristics of the output pulse, including spectral broadening and pulse stability. Using a photonic crystal fiber with a length of 10 cm, where the input pulse is a Gaussian pulse with a frequency of f = 200 fs, pump pulse energy E = 1.5 nJ, corresponding to a pump intensity of P = 7.5 kW, at a pump wavelength λ = 3500 nm, if the dispersion properties are adjusted so that the pump wavelength can shift from the normal dispersion region to the anomalous dispersion region, the obtained output pulse exhibits increased spectral width (corresponding to 2600 nm and 7000 nm). However, the output pulse, in this case, is characterized by higher noise and reduced stability. The research findings present a viable solution for modifying the characteristics of output pulses applicable to supercontinuum light sources.

Multimodality fire and smoke detection system

2024-08-26T04:15:20+00:00

Early smoke and fire detection is extremely important to prevent serious consequences for humans and property. A common solution is to utilize physical sensors such as gas detection sensors, smoke detection sensors, and temperature detection sensors caused by fire. However, the detection time of physical sensors is slower than combining multiple cues, especially combining with computer vision. In this paper, we propose a multi-modal fire and smoke detection solution that combines physical sensors (Sensor) and image sensors (Camera). In particular, our proposed method applies artificial intelligence (AI) and Internet of Things (IoT) to detect smoke and fire in the indoor environment. The knowledge distillation algorithm (KD) transfers from the full version of YOLO teacher models to the reduced version of YOLO model, whose detection accuracy is 10% smaller than the full version. The KD model is simpler, so it has a faster response time than the full model up to 8.22 (ms) and 51.56 (ms) when it runs on GPU and CPU, respectively.

Research on topological optimization in design of Drone components fabricated by 3D printing technologies

2024-04-22T02:49:08+00:00

Recently, drones have been widely used to perform tasks in different fields, such as military and agriculture. To improve exploitation performance, being compact and lightweight, drones are constantly designed and optimized. One of the current research directions in drone design is to optimize the structure and geometry of their main components, such as the arms and the body frame, and manufacture them using 3D printing. In this paper, the topology optimization and the geometrical optimization using lattice structures were investigated and applied to optimize the structure of the arms of a quadcopter Drone (DJI-f450) with the aid of Hyperworks software. The optimization design methods were performed according to the criteria of minimizing weight, increasing the rigidity and reliability of components. The results obtained show that all the methods considered enable the increase of stiffness and reliability while reducing the weight by at least 21.88% compared to the original structure. Among the studied optimization methods, the combination of topology and lattice optimization is more effective in increasing the rigidity and safety factor. The findings in this study confirm the necessity and performance of geometry optimization methods and 3D printing technologies to improve the product design and manufacturing process compared to traditional methods.

Research on building a mathematical model to describe the operation of a ball rotor separator

2024-08-26T04:17:10+00:00

The separator, to ensure safety for fuze, has many different shapes, such as a slider, rotating disc, and rotating ball. The ball rotor separator has a compact and simple structure. Thus, it is suitable for use with small-sized fuzes with high rotation speeds. In this article, the author has presented a mechanical model for an object rotating around a fixed point (geometric center of the separator), established a system of differential equations describing the motion of objects, and calculated and determined operating time for design research and testing.

Investigating the effect of temperature and strain rate on the microstructure of nanocrystalline CoCrFeMnNi high‑entropy alloy by molecular dynamics method

2024-08-26T04:16:52+00:00

The effect of temperature and strain rates on the microstructure development of a typical polycrystalline CoCrFeMnNi high entropy alloy was studied in molecular dynamics. Four typical temperatures of 300 K, 700 K, and 1100 K were selected. The results revealed that the peak stress and the tow stress decreased with the increases in formation temperatures, while the extent of twinning was found to be responsive to the temperatures. Furthermore, three strain rates of 1×10⁸/s, 5×10⁸/s, and 1×10⁹/s were chosen to explore the influence of strain rate on the microstructural behavior of the material at 300 K. It was found that both peak stress and tow stress increased with the strain rates.