Journal of Military Science and Technology

Air pollution forecasting: Application of machine learning models to estimate PM2.5 index

Nghiem Van Tinh, Pham Quang Hieu — Fri, 06 Dec 2024 00:00:00 +0000

In the context of ongoing industrialization, air pollution has become an urgent global problem, particularly severe in large cities such as Hanoi (Vietnam), Beijing (China), and others. Air pollution, especially the concentration of fine particulate matter (PM2.5), is not only harmful to human health but also has significant negative impacts on the environment, economy, and quality of life. This study aims to enhance the ability to predict air pollution levels more accurately. By using machine learning models, meteorologists can better predict air pollution levels and propose more effective mitigation solutions. The article utilizes a multivariate time series dataset, including meteorological and air pollution indices from Beijing, China, from 2010 to 2014. Machine learning models such as Lasso Regression, Support Vector Regression, Random Forest, XGBoost, and, notably, a Stack Model combining the four aforementioned models, are evaluated. The performance of these models is measured using statistical indicators such as Root Mean Square Error (RMSE), Mean Absolute Error (MAE), and Coefficient of Determination (R²). Among these models, the Stack model provides the most accurate predictions for the PM2.5 index.

Adaptive-based hierarchical sliding mode control for ball-balancing robots moving on an inclined plane

Fri, 06 Dec 2024 00:00:00 +0000

In contrast to managing a robot on a flat surface, controlling a balanced robot on a spherical wheel on an inclined surface is more challenging since the robot travelling up and down a slope has a higher chance of falling over. In this paper, the kinematic equation of the ball balancing robot (ballbot) is built as the learning method according to a 2D mathematical model. The authors use an adaptive-based hierarchical sliding mode control (AHSMC) based on Lyapunov theory to handle the target of a system whose parameters are undefined or change over time. The proposed sliding surfaces are demonstrated to be asymptotically stable and are validated through a simulation model implemented in Simscape software. The simulation results of the closed control design work correctly to control the motion of a ballbot when moving up the inclined surface.

Method of control of single channel aircraft by unipole relay steering gear

Pham Cong Tu, Nguyen Quang Vinh, Nguyen Van Son — Fri, 06 Dec 2024 00:00:00 +0000

To control an aircraft in space, aircraft usually have to use two steering gears, one for the range channel and one for the direction channel. However, with a single-channel aircraft, only a single steering gear is used for control. By rotating around the body at a stable speed, it is possible to control the aircraft in all directions with only a single steering. With the method of controlling the aircraft using a unipole relay steering, it will allow the use of a simple structure and the fast action of the relay steering, but reduce oscillations when the aircraft approaches the target. The article will analyze and evaluate the method of controlling a single-channel aircraft using a unipole relay steering gear. Compare it with the case when using other steering to give the advantages and disadvantages of the proposed method.

Sliding Mode Control for Stewart platform manipulators: A quasi-physical model-based approach

Tran Trung Kien, Vu Duc Cuong, Nguyen Danh Huy, Nguyen Trung Kien — Fri, 06 Dec 2024 00:00:00 +0000

This paper presents the design and implementation of a Sliding Mode Control (SMC) strategy for a 6-degree-of-freedom parallel robot, the Stewart Platform. The Stewart Platform is a type of parallel robot characterized by a structure consisting of six links connecting a fixed base to a movable platform, allowing for precise movement and control. This research begins with a detailed mathematical modeling of the Stewart Platform, capturing the system's complex kinematic and dynamic characteristics. Based on the system's dynamic model, the paper introduces a control method utilizing SMC for the Stewart Platform. Subsequently, a Simscape model, a simulation environment based on MATLAB, is provided to validate the performance and accuracy of the proposed control strategy. The simulations demonstrate significant improvements in the precision and stability of SMC in enhancing the operational efficiency of parallel robots. The simulation results are available at: https://youtu.be/7Y0hBNNKAZE.

Synthesizing electrical drive control system with several sliding surface reaching laws applied to manipulate Quadcopter

Le Khanh Thanh, Vu Quoc Huy — Fri, 06 Dec 2024 00:00:00 +0000

This paper studies on the stability of a variable structure control system operating in sliding mode using Lyapunov criteria and different sliding surface reaching speeds. This is a new research result that allows quantifying sliding surface parameters thanks to the system’s settling time and desired error. The paper also proposes a method for synthesizing a variable structure controller using a general sliding surface approach law and specifying some derivatives of the general sliding surface reaching law. Some simulations of controlling a Quadcopter motion channel have been performed in Matlab to demonstrate the proposed research results.

Solution for quick setup of improved TZK viewfinder integrated into mobile anti-aircraft fire control system

Pham Chi Thanh, Le Duc Anh, Vu Quoc Huy — Fri, 06 Dec 2024 00:00:00 +0000

The paper proposes a solution of supplementing tilt sensors and an electronic compass to the TZK viewfinder, integrated into the viewfinder’s data collection and processing system. The paper also proposes a new solution, which only uses the tilt angle at the time of setting up to ensure data security. Online tilt angle data processing is only intended to monitor attitude changes, to make a condition for resetting the viewfinder in the ground-fixed coordinate system. Assuming the target is attached to the endpoint of the line of sight vector, using geometry and Euler rotations, a quick setup algorithm and a reset algorithm are built. The target angle in the ground-fixed coordinate system is determined, providing input to the mobile anti-aircraft fire control system. The research results are mathematically rigorous and visually simulated in Matlab.

Flatness-based motion planning and a sliding mode control with a extended state observer for a gantry crane: a novel approach to payload positioning problems

Bui Thi Khanh Hoa, Hoang Thi Mai, Luu Thi Hue, Nguyen Tung Lam, Nguyen Danh Huy — Fri, 06 Dec 2024 00:00:00 +0000

This study proposes to produce a time-optimal motion controller for a single pendulum crane system based on the theory of construction so that the system transfers the load to the desired position while reducing vibration with variable variable rope length. The dynamics of the system is constructed by applying the Euler-Lagrange method. In addition, to improve robustness and noise effects, the study used a fixed-time extended state observer (ESO) and a sliding mode control (SMC). ESO provides an accurate estimate of the state and total disturbances in a fixed time. The expected trajectory is obtained by solving the optimal parameters of the flat output.

Modeling of grid-connected inverter using grid-forming technology

Nguyen Quang Minh, Cao Thanh Trung, Hoang Anh — Fri, 06 Dec 2024 00:00:00 +0000

Currently, grid-forming inverter technology is attracting attention and research investment worldwide, as it represents a critical step toward achieving a society powered entirely by renewable energy. However, foundational knowledge on this technology remains limited. This paper presents the control system structure for a grid-forming inverter with a simple design approach. First, a general state-space model of the system is developed to assess stability. Then, the system’s operational parameters are verified, and simulations are conducted on PSCAD software for further analysis. The results clarify the key concepts and structure of grid-forming technology, propose a method for stability assessment, and provide guidance on utilizing simulation tools for this system.

Design of energy balancing circuit for battery cells connected in series based on modifying the bidirectional Cuk converter

Nguyen Vinh Thuy, Nguyen Van Chi — Fri, 06 Dec 2024 00:00:00 +0000

This paper proposes a design of energy balance circuit for two adjacent Lithium-ion battery cells in the cell string based on the modifying of the bidirectional CuK converter principle. This design only uses one MOSFET to transfer energy between two cells in a direction controlled by the first relay, second relay controls the cutting energy balance circuit off the cells when they have the same energy level. This design overcomes some disadvantages caused by applying the principle of bidirectional CuK converter to design the energy balancing circuit, these are the need for a multiple level DC source to open MOSFETs and issue of the energy loss on the elements of energy balance circuit. This design is also easy to expand for the battery string with a large number of cells. The experimental results of online optimal energy balance control based on state of charge (SoC) feedback for 07 SAMSUNG 22P battery cells connected in series are presented to prove the efficiency of the energy balance circuit design for two adjacent cells proposed in this paper.

Building an object tracking algorithm based on image processing for UAV quadrotor

Pham Van Dat, Le Ba Chung, Hoang Quang Chinh — Fri, 06 Dec 2024 00:00:00 +0000

The paper presents the results of algorithm construction and the experimental control of object tracking based on image processing for quadrotor UAV using a dynamic model of quadrotor UAV, deep learning model and optimized for hardware system. The hardware system uses a depth camera, embedded computer to collect image data, object distance information and calculate, process to give control signals to the motors through the flight controller to ensure tracking and maintain distance between UAV and object. The results achieved in the paper can evaluate the ability to respond in real time to the problem of object tracking using image processing with hardware with limited resources.

Global sliding mode control integrated with extended state observer for wheel slip tracking

Fri, 06 Dec 2024 00:00:00 +0000

The Anti-lock Braking System (ABS) is crucial for vehicle safety by maintaining wheel traction during braking and preventing wheel lock-up. This study proposes an advanced Global Sliding Mode Control (GSMC) strategy to enhance ABS performance. The nonlinear global sliding mode of the surface is designed based on the exponential approach law. The method can eliminate the reaching phase compared with Sliding Mode Control (SMC), and guarantee the system robustness during the whole control process. The Extended state observer (ESO) is used in combination with the design of the GSMC in order to estimate the total uncertainty in the system. Simulation results demonstrate that the proposed global sliding mode control scheme enables the wheel slip-ratio to converge to optimal value quickly with the small oscillation, and has a relatively short braking distance and braking time, which is very suitable to prevent the wheel from being locked during braking.

Synthesis of synchronous filter for target tracking system of the self-guided infrared flying vehicle

Tran Duc Anh, Tran Huu Phuong, Vu Anh Hien — Fri, 06 Dec 2024 00:00:00 +0000

This article deals with research in the field of noise-based signal processing for target tracking systems of the self-guided infrared flying vehicle. The article conducts theoretical analysis, builds block diagrams, structural diagrams and describes the operating principle of the synchronous filter in low and high input frequency, and proposes a mathematical model of this filter. The simulation results, carried out in Matlab/Simulink and Atium environments, are the basis for designing the synchronous filter electrical circuit of the correction circuit board attached to the launch mechanism of the self-guided infrared flying vehicle.

A solution to regulate tilt angle for photovoltaic panels to improve the capability to harness power from photovoltaic power generation

Le Tien Phong — Fri, 06 Dec 2024 00:00:00 +0000

This study proposes two design methods for mechanical and control systems to improve the capability to generate power from photovoltaic power generation. The operating principle of photovoltaic power generation and the effect of solar irradiance on the ability to release electrons will be considered and analysed to make clear the role of the solar tracking system in the operating process. The mechanical design will be introduced for a two-axis system to track the movement of the sun at any time in a day and days in a year. The control system is designed to meet automatic operating requirements in real time using real-time module or information collected from light sensors. Hybrid servo-step motors will be used to rotate two axes with a fixed distance corresponding to the designed angle calculations that can help to have accurate movements and low power consumption. Proposed researches will be demonstrated by an experimental model created in Thai Nguyen University of Technology, Thai Nguyen University. This model was installed and tested in its operations for a long time to show the ability to apply scientific ideas to real systems as solar trackers.

Control of liquid sloshing container in horizontal motion by generating a trajectory based on the flatness theory

Fri, 06 Dec 2024 00:00:00 +0000

The oscillation of liquid inside a moving container is a complex nonlinear dynamic phenomenon that can induce instability in the fluid-containing system. This paper proposes a stabilization method for liquid surface oscillations at the initial and final points of the trajectory, utilizing flatness to establish the trajectory and constructing a tracking controller. The effectiveness of the proposed method is verified through simulation results.

Second order sliding mode control based on extended state observer for double pendulum overhead cranes

Nguyen Dinh Hiep, Vo Nhat Huy, Nguyen Danh Huy, Hoang Thi Mai — Fri, 06 Dec 2024 00:00:00 +0000

This study proposes a second order sliding mode controller based on an extended state observer for a 3D crane system with a double pendulum effect and constant rope length. A second order sliding mode controller requires an accurate model of the system's parameters. However, in practice, model parameters and external disturbances are difficult to determine in detail. Therefore, the extended state observer is designed to estimate the system state variables and the total disturbance. Finally, a sliding mode controller is developed with the signals taken from the observer. The proposed controller ensures stability according to Lyapunov function. Simulation results show that the proposed method ensures that the trolleys reach the desired trajectory while minimizing vibration even in the presence of disturbances and uncertain components.

A novel methodology design for matching network based on SIW technology for microwave power amplifiers

Dai Xuan Loi, Luong Duy Manh, Vu Le Ha — Fri, 06 Dec 2024 00:00:00 +0000

This paper presents a novel method for creating a matching network (MN) with filtering functionalities on substrate intergrated waveguide (SIW) using Complementary Split Ring Resonators (CSRR). It defines principles for modifying the MN impedance through adjustments to the parameters of the CSRR and SIW transmission line. Additionally, it demonstrates the practical implementation of this approach by designing an output MN for a high-frequency power amplifier operating at 6 GHz. The MN is configured with dimensions of 13.6 x 5.4 mm and exhibits an insertion loss of 1.26 dB.

Research on solution to expand the bandwidth of X-band waveguide bandpass filter applied in passive radar

Luu Duc Tho, Luong Van Trinh, Nguyen Cong Oai — Fri, 06 Dec 2024 00:00:00 +0000

Currently, ultra-high frequency filters are widely used in many different fields. In radar systems, filters play an important role in the transmit-receive line, but ensuring that the filter works in a wide frequency range and has low loss is a complex problem. In this paper, the authors present the results of research and design of a waveguide bandpass filter working in the frequency range of 8 to 12 GHz (X-band). The results of the analysis of the operating principle, calculation and simulation on CST 2019 software show that the bandpass filter operates in a wide frequency range, meeting the requirements of passive radar stations.

Comparison of analysis methods for separating and recognizing multicomponent radar signals

Nguyen Van Dat, Duong Van Minh, Nguyen Thi Phuong, Nguyen Manh Hung — Fri, 06 Dec 2024 00:00:00 +0000

This paper proposes a model for separating and recognizing a mixture of radar signals using combined multiresolution methods and convolution neural networks. The model involves three main steps: separating the signal into individual components using the Multiresolution analysis (MRA) methods: Empirical mode decomposition (EMD), Variational mode decomposition (VMD), and Maximal overlap discrete wavelet packet transform (MODWPT); transforming these components into the time-frequency domain using Wigner-Ville distribution (WVD) and storing them as images; and then feeding these images into the SqueezeNet for recognition. These multiresolution methods are then compared based on three criteria: The number of successful separations, the SNR ratio of the input signal, and the correlation between the separated signal components and the original signal components. Additionally, we evaluate the performance of the SqueezeNet with real-time signals.

An efficient solution for radio frequency measurement

Tran Dinh Lam, Vu Le Ha, Dai Xuan Loi, Luu Thi Thu Hong — Fri, 06 Dec 2024 00:00:00 +0000

Radio frequency determination is one of the important parameters in target detection, identification and classification. Some common technical solutions used to determine frequency are spectrum analysis by FFT transformation, direct frequency determination IFM (Instantaneous Frequency Measurement) and signal autocorrelation. This paper proposes a solution to determine radio target frequency applicable to target observation and tracking systems based on the hybrid technique between the effect of stacked filters and real-time spectrum analysis. The IFM-FFT hybrid solution proposed in the paper improves the accuracy of frequency detection and reduces the strictness in the design of stacked filters compared to the IFM solution. At the same time, compared to the pure FFT spectrum analysis solution, the IFM-FFT hybrid solution ensures faster detection time over a wide frequency range.

Study on dose calculation of low level laser in the treatment of chronic wounds

Fri, 06 Dec 2024 00:00:00 +0000

Chronic wounds have failed to progress through a timely repair sequence or one that proceeds through the wound-healing process without restoring anatomic and functional results. Common examples include pressure ulcers, diabetic ulcers, vascular ulcers,... These wounds cause pain and significantly impact patients' health, psychology, and finances, while also placing a burden on healthcare facilities for treatment. Low-level laser therapy has been proven to be an effective method for treating chronic wounds by accelerating the inflammatory phase and stimulating proliferation and healing. However, to meet therapeutic requirements, it is necessary to deliver the correct therapeutic dose (laser energy density). This study establishes a computational model to calculate the absorption and dispersion capabilities of lasers in skin tissue on the back and heel areas with various levels of damage. The purpose is to aid in calculating treatment dosages, enhancing effectiveness, and optimizing the treatment process for chronic wounds.

Efficient UAV localization using combined autoencoder and SIFT

Ngo Van Quan, Phan Huy Anh, Bui Thi Thanh Tam, Nguyen Chi Thanh — Fri, 06 Dec 2024 00:00:00 +0000

In GNSS-denied environments, accurate Unmanned Aerial (UAV) localization faces significant challenges. This paper introduces a vision-based localization method combining autoencoder and SIFT algorithms, referred to as AE+SIFT. The method compresses high-resolution map images into low-dimensional vectors, which are stored in a database for efficient retrieval. During the localization process, UAV images are encoded and matched with the database, followed by SIFT and homography projection for precise positioning. The AE+SIFT approach enhances localization accuracy, achieving an average coordinate error of 3.94 meters relative to the ground truth. Notably, when UAV images are misaligned with reference images, our method outperforms the existing AE method in terms of accuracy.

Design and calculate of wide-band mixer semiconductor on 130 nm CMOS technology

Phan Hong Minh, Nguyen Thi Thuy, Nguyen Truong Son — Fri, 06 Dec 2024 00:00:00 +0000

The article introduces a method of calculating and designing the parameters of the GilbertCell Mixer, which is made of CMOS components using the PDK Skywater 130nm process. The mixer is calculated, designed in principle and layout to work in the frequency range of 8 MHz ÷ 30 MHz, from which it is possible to evaluate the working parameters, limit the risks in the manufacturing process and apply them in practice in the field of designing specialized RF chips for radio communication devices using CMOS technology.

Applying closed-loop equations for kinematic analysis of an eight-bar walking mechanism

Dang Anh Tuan, Nguyen Thi Thu Linh — Fri, 06 Dec 2024 00:00:00 +0000

Bionic mechanisms are used in constructing robotic systems that perform complex tasks similar to the movement of animals. With advancements in scientific research and breakthroughs in simulation techniques and computational methods, the design of these systems has become increasingly detailed and refined. This paper proposes using the closed-loop method to analyze the operational characteristics of a wheelless walking mechanism designed to traverse complex terrains. In addition to evaluating fundamental factors affecting system operation, the study determines kinematic parameters such as leg trajectory, movement velocity, and tilt angle. The results demonstrate the effectiveness of numerical methods in analyzing and simulating real-world systems, thus extending the use of computational tools for analyzing similar linkages.

Optimum design of 3RUU parallel robot using improved Atlas method

Le Huu Hung, Pham Thanh Long — Fri, 06 Dec 2024 00:00:00 +0000

This article talks about using the improved Atlas method to optimally design the 3RUU parallel robot. The goal of this design is to determine the geometric dimensions of the robot so that the indicators of force and velocity conversion ratio between joint space and working space are best. There are three design criteria used in this study including robot dexterity, minimum velocity transmission coefficient and rigidity. The optimization method used in this study is the improved Atlas method. This method allows dividing multi-objective problems into single-objective problems and then superimposing feature Atlases to determine the optimal region. The novelty of the research is that the author will replace the Atlas superposition step with a technique called spread spectrum, this technique does not plot the characteristics like the original Atlas method but it superimposes representative values. number of the attribute under investigation on a predetermined grid of points on the robot's working space. The illustrative results in the article show that this method has potential for application on symmetric parallel robots with less than 4 variables needing to be synthesized.

Determining best dressing parameters for internal grinding SKD11 steel using EAMR technique

Truong Thi Thu Huong, Vu Duong, Le Thi Phuong Thao, Le Xuan Hung — Fri, 06 Dec 2024 00:00:00 +0000

The article conducts a research study on the use of Multi-Criteria Decision-Making (MCDM) in the internal grinding process of SKD11 tool steel. The aim is to identify the optimal input process parameters for the dressing process in order to minimize surface roughness (SR) and maximize wheel life (Lw). The EAMR strategy was employed to address the MCDM task, whereas the Entropy method was utilized to determine the weights of the criterion. The experiment also included the analysis of six input process parameters: coarse dressing depth, coarse dressing passes, fine dressing depth, fine dressing passes, non-feeding dressing, and dressing feed rate. The experiment was performed using an L16 orthogonal array and the Taguchi method. The wheel's durability and the roughness of the sample's surface were quantified and recorded for analysis in the MCDM problem. The research findings have identified the optimal dressing solutions for internal cylindrical grinding.).

Determination of shape and material thickness on dome of non-geodesic wound orthotropic composite pressure vessel

Dinh Van Hien, Tran Ngoc Thanh, Vu Tung Lam — Fri, 06 Dec 2024 00:00:00 +0000

In the composite pressure vessel winding technique, non-geodesic winding is a technique of spreading the yarn along a trajectory that deviates from the geodesic path (the shortest path connecting two points on the shell surface) a certain distance, but still ensures that the yarn does not slip on the shell surface. This technique is applied in winding pressure vessels with polar hole radii of two different domes. For cylindrically composite shell with domes, two important problems are: 1- determining the dome profile; 2- determining the composite shell thickness. This paper focuses on building a mathematical model to determine the above two problems based on the assumption that composite materials are orthogonal, in which, the problem of determining the dome profile is based on three conditions: 1- balanced shape, 2- no fiber slip, 3- minimum strain energy; while the thickness determination problem is performed using Tsai-Wu failure criterion. The results are the basis for calculation of structural and winding processing parameters of non-geodesic wound composite pressure vessels.

Research on the application of high-speed flight vehicles for testing aerospace electronics

Fri, 06 Dec 2024 00:00:00 +0000

In this study, the authors conducted calculations and testing of a high-speed flight vehicle, designated as TLM-515. TLM-515 achieved a peak velocity of approximately 750 m/s and a maximum altitude of around 10 km. The vehicle carried two critical, self-developed electronic devices: a GPS satellite navigation device and an inertial navigation sensor (INS), collectively referred to as onboard systems. The objective was to evaluate their independent and combined operational capabilities in high-speed flight conditions. Test results demonstrated that TLM-515 followed a stable trajectory, and the onboard systems effectively measured the vehicle's kinematic parameters, thereby assessing the functionality of the electronics in a high-speed environment. This solution has shown a high level of reliability, suggesting its potential applicability to similar experimental platforms.

Optimization of electric vehicle suspension parameters using improved artificial fish swarm algorithm

Nguyen Tien Dung, Bui Van Cuong, Le Van Quynh, Hoang Anh Tan — Fri, 06 Dec 2024 00:00:00 +0000

This study proposes a solution to reduce vertical vibrations and body pitching in response to random road surface excitations. To achieve these objectives, a half-vehicle model of an electric vehicle (EV) is developed to determine optimal parameters for both the EV suspension system and the driver's seat suspension system. An Improved Artificial Fish Swarm Algorithm (IAFSA) is implemented using MATLAB software to optimize these suspension parameters. The optimization aims to minimize the root mean square (RMS) values of three objective functions: vertical driver's seat acceleration (a_ws), vertical vehicle body acceleration (a_wb), and pitching vehicle body acceleration (a_wphi). The optimization results reveal that the values of these three objective functions decrease when using the optimized suspension parameters compared to the original suspension settings. Specifically, the a_ws, a_wb and a_wphi values are reduced by 15.44%, 11.46%, and 8.65%, respectively, when the vehicle travels on an ISO road class B at a speed of 20 m/s with a full load. Furthermore, the peak amplitude values of a_s, a_b, and a_phi in the frequency domain are also reduced with the optimized suspension parameters compared to the original settings under the specified conditions.

The law of increasing pressure of the wave interaction process in some mixtures liquid containing vapour bubbles

Nguyen Van Tuan, Le Xuan Long — Fri, 06 Dec 2024 00:00:00 +0000

The phenomenon of increasing pressure of the wave interaction process has a great influence on the transportation of oil in the energy industry, in hydraulic transmission systems of automobiles and specialized machinery. This paper presents the phenomenon of pressure increase due to the interaction between short waves in the mixture in the crude oil-containing vapour bubbles and in the liquid nitrogen-containing vapour bubbles. The wave interaction process is described by the system of hydro-thermodynamic equations. The numerical method is applied to calculate, study, and analyze the influence of the volume concentration of the vapour phase in the mixture on the pressure increase of the wave interaction process. From the obtained results on the dependence of the mixture pressure on the volume concentration of the vapour phase at the time of wave interaction, the pressure increase law of the short waves interaction process in some mixtures liquid containing vapour bubbles as above will be determined.

Numerical analysis of temperature behavior in solid and ventilated brake discs during repetitive braking

Do Van Quan, Le Van Quynh, Nguyen Minh Chau — Fri, 06 Dec 2024 00:00:00 +0000

The braking system is one of the crucial systems in a vehicle, responsible for decelerating it to a lower speed or bringing it to a complete stop. During braking, the friction between the brake pads and the brake disc generates heat, most of which is absorbed by the brake disc rather than dissipated. Consequently, the brake disc can rapidly accumulate significant heat, especially during repeated cyclical braking, leading to high-temperature regions. Under these conditions, several negative effects, such as brake disc wear, cracking, and reduced braking torque, may occur. This paper aims to compare the thermal behavior of solid and ventilated brake discs under repeated cyclical braking. Numerical simulations were conducted using ANSYS software, revealing that the maximum temperatures on the solid and ventilated discs during the final braking cycle were 252.61 °C and 221.12 °C, respectively. Therefore, the maximum temperature on the ventilated disc is approximately 12.5% lower than on the solid disc. These findings demonstrate that ventilated discs are effective in demanding conditions, consistently ensuring a high level of safety.

Optimization of structural parameters of the warhead to the penetration ability of the shaped charge

Nguyen Dinh Linh, Le Hai Thuong, Nguyen Xuan Thanh — Fri, 06 Dec 2024 00:00:00 +0000

The study of the rational selection of structural parameters for shaped charge warheads to achieve maximum penetration power is always a pressing issue that has received significant research attention. In this paper, the authors use a method for calculating the penetration power of shaped charges that takes into account the detonation position, combined with the Gravitational Search Algorithm (GSA) and the Autodyn 2D simulation method, to optimize the structure of a 110 mm shaped charge warhead by varying the following parameters: the half-angle of the liner cone α₀, which varies within the range of [25°; 30°]; the height of the liner cone H, varying within the range of [87 mm; 90 mm]; the x-coordinate of the secondary detonation center x_T, varying within the range of [21 mm; 27 mm]; and the y-coordinate of the secondary detonation center y_T, varying within the range of [40 mm; 47 mm]. This initial research has identified a parameter set [α₀; H; x_T; y_T] that achieves a maximum penetration depth of b = 717.98 mm.

Design, fabrication of launch tube of man-portable flight equipment made of composite material

Dinh Van Hien, Tang Xuan Long — Fri, 06 Dec 2024 00:00:00 +0000

The launch tube is an important part of the launch assembly, along with the launch motor helping the flight equipment move in a predetermined direction and reach a certain initial speed. In addition, the launch tube also serves as a storage tube for flight equipment in storage and transportation. For man-portable flight equipment, due to the requirement for quick combat, the launch tube is a disposable tube. The tube must be light in weight to be easy to carry and use, but must be durable enough under the pressure of combustion products from the launch motor. Most man-portable flight equipment in the world use launch tubes made from high-strength fiber-reinforced polymer composite materials because they can satisfy the above requirements that are difficult to meet using metal materials on mass. This paper focuses on researching the design of the composite launch tube structure of man-portable flight equipment based on sample reference and testing the launch tube's strength. Next, proceed to fabricate the launch tube from glass fiber-reinforced epoxy composite material and test it.

Synthesis of polyamide-based RO membranes for saline water treatment

Fri, 06 Dec 2024 00:00:00 +0000

Reverse osmosis (RO) technology is a widely used method for converting seawater into fresh water, known for its high efficiency and broad applications. This study focuses on optimizing the synthesis conditions for polyamide (PA) membranes, including the concentrations of m-phenylenediamine (MPD) and trimesoyl chloride (TMC), the choice of solvent, soaking time, and reaction time. FTIR and SEM analysis confirmed the successful synthesis of the PA layer and revealed that the surface morphology of the membrane was significantly influenced by synthesis conditions. Mechanical testing demonstrated that the optimized membranes exhibited high tensile strength (41.18 MPa) and low elongation at break (11.69%), indicating a robust but relatively brittle material. The study determined that the optimal conditions were 1.0 wt.% MPD and 0.1 wt.% TMC, hexane as a solvent, a soaking time of 2 min, and a reaction time of 60 sec, achieving a maximum salt rejection of 86.45%. These findings are critical for enhancing RO membrane efficiency and addressing the global demand for clean water.

Synthesis of Ce/graphene oxide modified with octyl amine nanocomposite (Ce-Imi/GO-OA) for the application of creating protective coatings against metal corrosion

Do Thi Thuy, Ha Quoc Bang, Nguyen Huong Giang, Tran Thi Thuy, Nguyen Huu Van — Fri, 06 Dec 2024 00:00:00 +0000

This article presents a method for synthesizing nanocomposite materials that protect against metal corrosion using a cerium modified 2-methylimidazole and graphene oxide modified octyl amine (GO-OA), denoted as Ce-Imi/GO-OA. The structural morphology of the material is evaluated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TGA). The corrosion protection capability of the material is evaluated using the Tafel curve method, electrochemical impedance spectroscopy (EIS), and accelerated salt spray testing according to ASTM B-117 standards. The research results show that Ce-Imi/GO-OA has a metal protection efficiency of 96.4%. The epoxy coating containing Ce-Imi/GO-OA has the ability to protect the metal for up to 90 days when immersed in a 3.5% NaCl solution. Research results show that Ce-Imi/GO-OA has good dispersion ability in epoxy resin, forming a protective film that prevents the infiltration of corrosive environments.

Synthesis and characterization of F127-Glu@ZnO nanogel material for cisplatin drug delivery application

Nguyen Ngoc Son, Vu Minh Thanh, Nguyen Thi Huong — Fri, 06 Dec 2024 00:00:00 +0000

A novel F127-Glu@ZnO nanogel was synthesized for cisplatin delivery by functionalizing ZnO nanoparticles with L-glutamic acid (Glu) and grafting Pluronic onto Glu via urethane linkages. FT-IR and ¹H-NMR confirmed successful synthesis, while TEM characterized morphology. The nanogel exhibited pH-responsive drug release, accelerating cisplatin release in acidic environments. This suggests its potential as a smart drug delivery system for improving therapeutic efficacy and reducing side effects in cancer treatment.

Synthesis and evaluation of fluorescence spectra and mass spectra of some complexes formed by lanthanides with benzoate and 2,2'-dipyridine-N-oxide ligands

Nguyen Thi Hien Lan, Tran Quoc Toan — Fri, 06 Dec 2024 00:00:00 +0000

Three series of lanthanide (III) complexes coodinated with benzoate and 2,2’-dipyridine-N-oxide were subjected to mass spectrometric and emission spectra analysis. These complexes were synthesized with a synthetic yield of 85%. Mass spectroscopy findings show that the synthesized complexes are monomers, they are represented by the general formula of Ln(Ben)₂(DipyrO)₂(H₂O)₂ (Ln: Tb, Dy, Yb; Ben: Benzoate; DipyrO: 2,2’-dipyridine-N-oxide). The emission spectra of the Tb(Ben)₂(DipyrO)₂(H₂O)₂ display three bands arising from the ⁵D₄ → ⁷F₅ dominant transition located at 545 nm, the weaker ⁵D₄ → ⁷F₆, ⁵D₄ → ⁷F₄ transitions located at 490 and 587 nm, respectively. The luminescent spectra of the Dy(Ben)₂(DipyrO)₂(H₂O)₂ displayed two bands at 480 and 576 nm, arising from ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_11/2 transitions, respectively. The ⁵D₄ → ⁷F₅ emission lifetime in Tb(Ben)₂(DipyrO)₂(H₂O)₂ is t = 0,07609 ± 0,00804 ms. The ⁴F_9/2 → ⁶H_11/2 emission lifetime in Dy(Ben)₂(DipyrO)₂(H₂O)₂ is t = 0,06943 ± 0,00706 ms. The results of our study demonstrate that these complexes exhibit room-temperature photoluminescence.

Synthesis adsorbent materials from coffee husk and determine the efficient removal Chromium(VI) in water

Fri, 06 Dec 2024 00:00:00 +0000

This study introduces the results of the research on the construction of the process of making adsorbent materials from coffee husk and evaluates the applicability to treat Cr(VI) in water. The adsorbent material is made through 2 stages: Pyrolysis at 350 ^oC, 1 h and impregnation with KOH 1 M, 24 h, pyrolysis 700 ^oC, 2 h. Materials were evaluated for their properties and factors that affect the adsorption process. The results showed that the treatment efficiency of Cr(VI) in water reached 98,72% at pH 3, 180 minutes and the adsorption material ratio was 0,5 g/100 mL. The pseudo-sencond-order kinetic model and the Langmuir isothermal adsorption model were suitable for describing the adsorption process of materials with Cr(VI).

Research on alloying the Cu-Ni-Sn system equivalent to grade C72500 in vacuum induction furnace

Ninh Duc Ha, Tran Van Cuong, Ngo Minh Tien, Trieu Khuong — Fri, 06 Dec 2024 00:00:00 +0000

In this article, research on smelting technology of elastomeric copper alloy of Cu-Ni-Sn system grade C72500 in vacuum induction furnace and some results of studying the structure and mechanical properties of C72500 alloy were shown. The C72500 alloy was smelted in a vacuum medium frequency furnace with a small burning rate and high cleanliness. Some methods to evaluate by determining structure, mechanical properties as: EDX spectroscopy analyzes element content, Optical microscope equipment to determine microscopic structure, ultrasonic equipment to evaluate defects and equipment to test mechanical properties. The after-casting alloy has a chemical composition and mechanical properties equivalent to imported copper alloys according to ASTM B122/B122M-20 standards, single α phase structure, good ductility but low strength, elongation 62.2%, tensile limit 301.43 MPa, yield limit 171 MPa and hardness distributed along the sample, high on the outside (82.4 HV) and low in the center (73.4 HV), is used in manufacturing elastic, abrasion and corrosion resistant parts.

Investigation of toxin genes and potential to control early shrimp mortality disease of chitosan on some Vibrio parahaemolyticus strains isolated from Mekong Delta

Fri, 06 Dec 2024 00:00:00 +0000

Acute Hepatopancreatic Necrosis Disease (AHPND) is a disease that induces mass early mortality in shrimp caused by Vibrio parahaemolyticus. This bacterium is capable of secreting biofilm - the main element in the host invasion mechanism and also protects V. parahaemolyticus from anti-bacterial agents, especially antibiotics. In this study, 03 strains of V. parahaemolyticus isolated from infected shrimp samples were investigated for toxin genes. They had the toxR gene and lacked tdh, trh and pPVA3-1 virulence plasmid genes. Chitosan was used to inhibit and destroy their biofilm biosynthesis in order to prevent AHPND. The minimum chitosan concentration inhibiting biofilm biosynthesis was 2 g/L. At 3 g/L, chitosan was capable of destroying 87.78 - 88.74% of the formed film. Biofilm analysis before and after treatment with chitosan showed that the EPS rate after treatment was reduced by 68-72.73% compared to that before treatment. The results demonstrated the potential of chitosan in the prevention of AHPND.

Characteristics of pectin extracted from dragon fruit stems in Binh Thuan, Vietnam and gel formation method

Fri, 06 Dec 2024 00:00:00 +0000

Pectin was extracted from dragon fruit stems under conditions of pH 3, at a temperature of 70 °C for 180 minutes, yielding the highest extraction efficiency at 19.52%. The characteristic properties of pectin were also investigated to guide applications in gel formation and to identify its chemical structure. The moisture content was 10.5%, meeting the recommended moisture range of around 12% as suggested by the pectin manufacturers' association. FTIR analysis identified characteristic functional groups in the pectin structure such as O-H, carboxyl (C=O), and C-H groups. The FTIR results also determined the degree of esterification (DE) to be 32.1%, classifying it as low methoxyl pectin (LMP), suitable for gel formation applications with divalent ions. The analysis of sugar content in dragon fruit pectin also provided preliminary insights into its chemical structure.

Study on the efficiency of mononitrotoluene treatment in aqueous environments using the Sono-Photo-Fenton process combined with zero-valent iron nanoparticle (nZVI) catalysts

Fri, 06 Dec 2024 00:00:00 +0000

The wastewater containing Mononitrotoluene (MNT) has adverse effects on human health, living organisms, and the surrounding environment. In this study, the efficiency of MNT treatment in water using the Sono-Photo-Fenton-like process combined with zero-valent iron nanoparticles (nZVI) was evaluated. The effects of pH, H2O2 concentration, nZVI concentration, and reaction time on the treatment efficiency were investigated using experimental design through the Response Surface Methodology (RSM). The study results showed that the treatment efficiency of MNT using the Sono-Photo-Fenton process combined with nZVI reached 100% under the conditions of pH = 2, initial MNT concentration of 100 mg/L, nZVI concentration C_nZVI = 0.5 mM, C_H2O2 = 5 mM and a reaction time of 30 minutes.

Construction and expression of gene coding MHETase in E. coli

Dinh Thi Hoa, Le Thi Thu Hong, Le Minh Tri, Pham Kien Cuong, To Lan Anh — Fri, 06 Dec 2024 00:00:00 +0000

Polyethylene terephthalate (PET) is a type of synthetic plastic widely used in many applications, especially packaging production. With the increasing production, consumption rates, and a short life cycle, the abundant amount of waste from PET plastic in the environment seriously affects human health as well as other living organisms. Currently, plastic treatment solutions that are safe, sustainable, and environmentally friendly have received much attention, especially biodegradation methods using natural microorganisms or enzymes for plastic treatment. To date, PETase and MHETase are two enzymes that have been studied with great potential in PET plastic degradation. In this study, we have successfully designed and expressed the gene encoding the enzyme MHETase using the E. coli BL21(DE3) expression system. The recombinant strain harboring the plasmid pET22b(+)-MHETase was cultured in LB medium containing 100 µg/mL Ampicillin, and extracellular protein was collected after 48 hours with the induction of 0.1 mM IPTG and cultivation at 30 °C. The results of the analysis by Western-blotting and SDS-PAGE protein electrophoresis showed that the expressed MHETase had a molecular weight of about 63 kDa, which is equivalent to the theoretical molecular weight. The specific activity of recombinant MHETase enzyme obtained by precipitation of (NH₄)₂SO₄ salt was 85.88 U/mL. These results show the potential of MHETase enzyme for application in the degradation of PET plastic waste.