Journal of Military Science and Technology

An ensemble model with feature selection for nearshore wave forecasting

Chu Thi Quyen, Ngo Thi Thanh Hoa, Nguyen Thi Cam Ngoan — Mon, 25 Aug 2025 00:00:00 +0000

The study proposes an ensemble one-week ahead Wave Forecast of Nearshore Waves (OWFNW) framework for managing shipping and construction in marine work sites. The framework uses XGBoost with feature selection (FS_XGBoost) for forecasting at 5 stations on the Japanese coast. XGBoost-based wave models are developed for each station, transforming global wave data into nearshore wave predictions. Models are trained using four different training sets from the Japan Meteorological Agency (JMA), National Oceanic and Atmospheric Administration (NOAA), European Centre for Medium-Range Weather Forecasts (ECMWF) and Nationwide Ocean Wave information network for Ports and HarbourS (NOWPHAS). The results indicate that selecting features enhances the model's prediction accuracy and refining prediction errors. The methodology can be applied to other nearshore seas where global wave forecast data is available.

Ontology-based query graph matching

Doan Quang Tu — Mon, 25 Aug 2025 00:00:00 +0000

The requirement for business competition among organizations has become more complicated in the past decade. One of these issues is how to react and response to queries from clients with the aim of producing quick and timely decision-making. To address this problem, this paper proposes a framework for identifying the frequent queries from multiple sources. The main contribution of this work is (1) query matching based on the ontology. In fact, query matching has been widely explored using various methods, most of which are based on a labeling approach and utilize isomorphism to map a query to subgraphs in a graph database. However, these traditional methods may not capture enough semantic similarity when mapping terms together. Ontology-based matching can address this issue more effectively than mere labeling isomorphism. In this work, three pruning techniques and their combination within dynamically weighted sets of vertex-associated elements are proposed. In addition, (2) a subgraph/subontologies clustering technique is recommended to extract the results of the framework. This technique is based on an existing clustering method, but requires improvements in the data processing step to be applicable to clustering subontologies/subgraph objects. Finally, (3) we experimentally verify the effectiveness and efficiency of our pruning techniques using synthetic data and compare the techniques themselves.

Application of the SQP algorithm in leader–follower formation control

Duong Phu Tuan, Nguyen Tuan Minh, Quang Vịnh Nguyễn — Mon, 25 Aug 2025 00:00:00 +0000

This paper proposes the application of the Sequential Quadratic Programming (SQP) algorithm to control a group of omnidirectional mobile robots using the Leader-Follower model. The method includes predicting the group’s kinematics, formulating a distributed model predictive control (DMPC) problem with a cost function comprising components for formation maintenance, trajectory tracking, and collision avoidance. The cost function is then optimized in real time using the SQP algorithm. In simulations, Gaussian noise is introduced into the states and control signals to evaluate the method’s effectiveness under real-world deployment conditions.

Synthesize control signal to electric drive systems of 2-wheel autonomous robots using PA-BLDC actuator

Le Ba Yen, Vu Quoc Huy — Mon, 25 Aug 2025 00:00:00 +0000

The paper studies the synthesis of a control signal generator for electric drive systems in 2-wheel autonomous robots using brushless DC motors (BLDC) with power amplifiers (PA). The mathematical and discrete structure of the PA input control signal generation block based on differential equations is proposed, ensuring the drive system tracks the guide element with high accuracy. Mathematical analysis has proven that the system is stable and converges to the desired value with small tracking errors. Simulations are performed in MATLAB Simulink with different guidance signals varying over time.

Synthesis of nonlinear robust control for aerial vehicles under parameter uncertainties

Nguyen Viet Phuong, Nguyen Duy Khanh — Mon, 25 Aug 2025 00:00:00 +0000

This paper proposes a nonlinear robust control strategy for the longitudinal motion channel of an aerial vehicle (AV) to enhance flight control quality under parameter uncertainties. A mathematical model of the control object is developed, and a robust nonlinear controller is synthesized using sliding mode control (SMC) combined with a reference model. The controller parameters are designed based on Lyapunov stability theory, ensuring the robust stability of the closed-loop system. A linear modal controller is developed to compare with the proposed nonlinear controller. Comparative simulations conducted in MATLAB/Simulink highlight the superior performance of the proposed controller in terms of tracking accuracy and robustness.

Designing an ECG signal measurement and analysis system using SVM algorithm for arrhythmia classification

Pham Van Nam, Nguyen Thu Ha, Pham Van Hung, Pham Van Minh, Tran Thi Hang — Mon, 25 Aug 2025 00:00:00 +0000

This paper introduces a hardware device designed for measuring electrocardiogram (ECG) signals, integrated with a remote system for automated signal analysis, facilitating health monitoring and heart disease diagnosis by doctors. The device transmits ECG signals in real-time to a server equipped with software for analyzing and classifying ECG signals using the Support Vector Machine (SVM) algorithm. Hermite basis functions are employed to generate feature vectors. The proposed solution has been validated using ECG signals from the MIT-BIH (Massachusetts Institute of Technology, Boston’s Beth Israel Hospital) database, achieving a 5.07% error rate in classifying seven types of heart rhythms. The SVM algorithm demonstrates high speed and suitability for server-based data classification needs.

Compact Ku-band monopulse microstrip stacked patch array antenna with hybrid power divider system

Le Nhu Thai, Le Thi Hang, Nguyen Hoai Son — Mon, 25 Aug 2025 00:00:00 +0000

This article will present an array antenna system with a compact size (diameter 190 mm) for a monopulse tracking application working in the Ku band, suitable for placement airborne where there is not much space. The antenna system consists of a monopulse comparator, a power divider system, and four subarray antennas. The monopulse comparator and part of the hybrid power divider are designed on the rectangular dielectric waveguide (RDW). The other part of the power divider and antenna element array is designed on the PCB substrate. The two parts of the power divider system are connected to each other through coaxial cables. Simulation results of the antenna system are obtained as follows: impedance bandwidth (VSWR < 1.8) is about 9%; SLL of the radiation pattern of an array antenna using an unequal power divider system with Taylor distribution (SLL= -20 dB, n = 4) at full range frequency is less than -20 dB. The realized gain of the sum beam is 28 dBi at the center frequency, while the zero depth of the difference beam is better than 20 dB. The excellent features of the proposed design make it a good candidate for two-dimensional monopulse tracking applications.

An enhanced random noise suppression method for fiber optic gyroscopes to improve gyrocompass performance

Nguyen Trong Yen, Nguyen Sy Long, Vu Doan Ket — Mon, 25 Aug 2025 00:00:00 +0000

This paper presents a method for reducing random noise and zero-bias instability in the signal of a fiber optic gyroscope, based on a hybrid algorithm that combines an autoregressive mathematical model with an adaptive Kalman filter using a Sage sliding window. The results of the study demonstrate that this approach shortens the gyrocompass initialization time while maintaining the accuracy of defining initial orientation parameters, particularly the initial azimuth angle. Consequently, it enhances the overall performance of the gyrocompass in strapdown inertial navigation systems, especially in scenarios requiring rapid startup.

Investigation of the effects of heat treatment on the microstructure and mechanical properties of Pb-Sb alloy used in fabrication of anode spines for high-capacity lead-acid batteries

Mon, 25 Aug 2025 00:00:00 +0000

The as-cast Pb-Sb alloy typically exhibits a heterogeneous microstructure and significant residual stress, rendering it susceptible to structural failure under external mechanical loads. This study demonstrates that heat treatment effectively homogenizes the microstructure, eliminates residual stress, and enhances the alloy's suitability for subsequent processing stages in the fabrication of anode electrodes for high-capacity lead-acid batteries. Post-heat treatment, the Pb-Sb alloy achieves an average hardness of 13.4 HV, a tensile strength of 31.67 MPa, and an equiaxed grain structure with an average grain size of 0.0164 mm.

Development of biodegradable lubricating grease for application in specialized equipment operating under marine environmental conditions

Tran Van Hien, Do Thi Thuy — Mon, 25 Aug 2025 00:00:00 +0000

Lubricating greases play a crucial role in protecting and maintaining the stable operation of equipment, particularly under the harsh and corrosive conditions of marine environments. Most currently available greases are formulated from mineral oils, which are non-biodegradable and pose serious environmental pollution risks. In response to the increasing demand for environmentally friendly alternatives, especially in marine environments where various military devices operate, the development of biodegradable lubricating greases has become a necessity. This study presents the synthesis and evaluation of a biodegradable grease formulated using castor oil as the base oil, lithium 12-hydroxystearate soap as the thickener, and functional additives with anti-corrosion and anti-wear properties. The grease was prepared with a thickener-to-base oil ratio of 14:86 wt.% and temperature processed at 220–230 ^oC, resulting in a stable structure and high homogeneity. Salt spray test results demonstrated a significant improvement in metal surface protection. Additionally, the grease exhibited a load-carrying capacity of 315 kg and a biodegradability exceeding 70%. The results indicate that the grease offers excellent lubricating and protective properties and high biodegradability, making it suitable for equipment operating in marine environments.

Evaluation of nitrate removal efficiency from aqueous solutions using modified biochar derived from coffee husk

Mon, 25 Aug 2025 00:00:00 +0000

This study presents the fabrication and evaluation of the nitrate adsorption capacity of modified biochar derived from coffee husk. The coffee husks were initially pyrolyzed at 350 °C for 1 hour, then soaked in 1 M KOH solution for 24 hours, followed by a second pyrolysis step at 700 °C for 2 hours. The resulting biochar was characterized using FT-IR, BET, and SEM techniques, and its nitrate removal efficiency from aqueous solutions was investigated. The highest nitrate removal efficiency (82.38%) was achieved under the following conditions: pH 3, biochar dosage of 1,5 g/100 mL, nitrate concentration of 50 mg/L, and reaction time of 210 minutes. The pseudo-first-order kinetic model and the Langmuir isotherm model were applied to describe the adsorption behavior, showing good agreement with the experimental data.

Research on the manufacturing of Fe2O3/TiO2-based adsorbent granules for application in treating Pb²⁺-contaminated water

Ngo Minh Tien, Tran Van Chinh — Mon, 25 Aug 2025 00:00:00 +0000

In this paper, Fe₂O₃/TiO₂ adsorbent granules were fabricated via a drum-type granulation method with bentonite as a binder. The granulation process included three steps: mixing Fe₂O₃/TiO₂mixture of powder and fine coal dust into a homogeneous mixture, granulating by spraying water mist, drying the beads, and calcining at 500 ^oC for 1 h to form pores. The characteristic structures of composite materials after fabrication are evaluated by various methods, such as X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. The performance evaluation of the fabricated adsorbent granulation for removing Pb²⁺ from polluted water was studied using a fixed-bed adsorption column. The factors affecting the adsorption performance, such as height of the adsorption column, flow rate, and inlet Pb²⁺concentration, were determined. In column mode, the longest exit time was 450 minutes, the saturation time was 723 minutes, and the adsorption efficiency was 78.202% at the initial concentration of 5 mg/l, column height of 16 cm, and flow rate of 5 ml/min. The adsorption data with three well-established fixed-bed adsorption models, namely the Adam-Bohart, Thomas, and Yoon-Nelson models, with a correlation coefficient, R² > 0.95.

Effect of some factors on the electrolysis production of sodium perchlorate from sodium chlorate using PbO2/Pb-Ti electrode

Nguyen Ba Ngoc — Mon, 25 Aug 2025 00:00:00 +0000

The electrolysis process of sodium perchlorate production from sodium chlorate using PbO₂/Pb-Ti electrode was studied by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and electrolysis efficiency evaluation. The results showed that the technological parameters (sodium chlorate concentration, temperature, electrolyte current density, additive content and pH) strongly affected the polarization, charge transfer resistance and electrolysis efficiency. Therefore, the appropriate technological mode for the electrolysis process was selected as: NaClO₃ concentration 300 - 600 g/L; temperature 50 ^oC; current density 0.15 - 0.2 A/cm²; NaF additive concentration 1-2 g/L; solution pH 7.

Research on methods for measuring and controlling the modulation index of a frequency-modulated interferometer for high-precision displacement measurement

Hoang Anh Tu, Vu Thanh Tung, Pham Anh Tuan — Mon, 25 Aug 2025 00:00:00 +0000

This paper presents the theoretical foundation combined with experimental implementation to develop an algorithm for controlling and measuring the modulation index (m) of a Frequency-Modulated Interferometer (FMI) used for high-precision displacement measurements. In FMI-based displacement measurement systems, the modulation index m and synchronous demodulators (Lock-in Amplifiers – LIAs) are two critical factors that distinguish this method from traditional interferometric techniques. While the modulation index m determines the measurement range limit, the LIAs ensure high accuracy within that range. In FMI systems, the modulation index is embedded in all harmonic components. When measuring over a large range, the harmonic amplitudes vary, causing m to change with displacement, which reduces the signal-to-noise ratio (SNR) of the interferometric signal pairs and consequently degrades measurement accuracy. A method for controlling the value of m is proposed based on the relationship between the initial measurement range, m, and Bessel functions. Accordingly, the quantitative value of m can also be accurately measured based on the intensity ratios of consecutive even and odd interferometric signal pairs. An experimental verification of the method was conducted with an initial measurement range of 25 cm. The modulation index m was successfully controlled and measured as m = 2.575, then adjusted to reach the special value m = 2.631.

Research on optimization of surface roughness of aspherical aluminum during Single-Point Diamond Turning using BBK model and PSO algorithm

Dao Van Duong, Nguyen Kim Hung, Ngo Van Tuan, Vu Thi Khanh Van, Duong Xuan Bien — Mon, 25 Aug 2025 00:00:00 +0000

The paper presents the results of optimizing the surface quality of aspheric aluminum during Single Point Diamond Turning (SPDT) based on the Box-Behnken Design (BBD) experimental method. The experimental dataset consists of 15 experiments established from the BBK model, supported by the ANOVA module in the specialized software DESIGN EXPERT. The objective function for roughness was established, resulting in a second-order multivariable regression equation that defines the roughness of the aspheric surface based on the data obtained after conducting all experiments. The objective function is formed based on the relationship between the roughness of the aspheric surface and the cutting parameters: spindle speed (n - RPM); feed rate (F - mm/min); and depth of cut (ap - mm). The modeling results, with a reliability of R² =0.9536, show a high correlation between the model data and the experimental values. By using the Particle Swarm Optimization (PSO) algorithm, the optimal surface roughness value achieved is 0.8 nm, obtained under the machining conditions of n = 2000 RPM, F = 8 mm/min, and ap = 4.2 µm. This study is significant for enhancing the optical surface quality in ultra-precision machining and provides a reliable foundation for building experimental models to optimize and accurately assess the machining process.

Study on a two-step polishing method using pulsed fiber laser for SKD11 tool steel components

Le Van Van, Vu Thanh Tung, Trinh Quang Hung, Phan Tien Thanh, Tran Van Chau — Mon, 25 Aug 2025 00:00:00 +0000

In this study, the authors propose and experimentally investigate a two-step polishing technique using a medium power pulsed fiber laser for cold work die components made of SKD11 tool steel. The objective is to improve the surface finish after milling by applying a high-precision laser polishing process that enables efficient and scalable automation. The experiments employed a pulsed fiber laser source with a maximum power of 35 W and a wavelength of 1064 nm, combined with a galvo scanning head and a digital control system. The polishing was performed under argon shielding gas with various scanning parameters. The study focused on evaluating the effects of laser power and the number of scanning passes on surface morphology, roughness, and near-surface microstructure. Results showed that the two-step polishing strategy, starting with high power laser passes (35 W) to remove major surface peaks, followed by low power passes (21 W) to smooth finer irregularities, effectively reduced surface roughness R_a from ~ 4.5 µm to ~ 1.2 µm (~73% reduction). Microstructural observations revealed phase transformations in the surface layer, with the formation of austenitic structures induced by the high-energy laser pulses. This study highlights the effectiveness of two-step pulsed laser polishing for difficult-to-machine materials like SKD11 and opens promising prospects for its application in precision mold manufacturing and automated surface finishing processes.

Study on the effect of rotating shaped charge liner material on penetration depth using the SPH numerical simulation method

Bui Xuan Son, Phung Van Cuong, Do Van Minh, Hoang Van Cuong, Dang Hong Duy — Mon, 25 Aug 2025 00:00:00 +0000

In this paper, the effect of liner material on the penetration capability of rotating shaped charge warheads was investigated. The authors employed 3D simulations using the Smoothed Particle Hydrodynamics (SPH) mesh-free method in Ansys Autodyn to study the influence of liner materials on rotating shaped charge warheads. The subject of study is a 40 mm caliber shaped charge warhead, with two liner material options: copper and steel. The numerical simulations were conducted at different rotational speeds about the warhead’s axis of symmetry: non-rotating, 2000 rpm, 4000 rpm, 6000 rpm, 8000 rpm, 10000 rpm, 12000 rpm, and 14000 rpm. The simulation results indicate that as rotational speed increases, the penetration depth into steel decreases. Copper liners exhibit superior steel penetration compared to steel liners. However, when the rotational speed reaches 10000 rpm, the penetration depth of the copper-lined warhead is not significantly greater than that of the steel-lined warhead. This research method can be applied to optimize the structural design of rotating shaped charge warheads.

Design of cooled MWIR continuous zoom optical system for long-range surveillance

Le Vu Nam, Pham Dinh Quy, Nguyen Thu Cam — Mon, 25 Aug 2025 00:00:00 +0000

The continuous zoom optical system based on the cooled infrared detector can achieve high-quality imaging in multiple FOVs. Based on the continuous zoom theoretical model, this paper designs a MWIR continuous zoom athermal optical system consisting of only six lenses. The system has an F# of 4.0, a working range of 3.4 - 4.9 μm, a field of view ranging from 21.8°×17.5° to 1.6°×1.3°. All six lenses in the optical system contain aspherical surfaces with two diffraction surfaces to eliminate aberrations, optimizing the size and weight. The optical system compensates for temperature through an active focusing mechanism. The MWIR continuous zoom optical system has a compact structure and good imaging quality in the whole FOV in the temperature range of - 10 ℃ ~ + 60 ℃.

Optimization of adaptive nonlinear aspherical microlens using ZEMAX

Pham Thanh Quang, Ho Quang Quy, Tran Quoc Tuan — Mon, 25 Aug 2025 00:00:00 +0000

This paper presents a comprehensive analysis of a thin plate of nonlinear medium (TPNM) irradiated by a laser Gaussian beam (LGB), which functions as a tunable nonlinear aspherical micro lens (NAML). When positioned at the beam waist of the LGB, the TPNM behaves as a Kerr-based lens with variable curvature and conic coefficient. Analytical expressions for the vertex curvature radius and conic coefficient are derived based on design parameters such as beam waist radius, peak intensity, nonlinear coefficient of refractive index, and physical thickness of TPNM. To verify and optimize lens performance, the optical design software ZEMAX is employed to extract and evaluate optical aberration, spot diagrams, and wavefront error. The optimization significantly reduces aberrations, spot size, and wavefront error, thereby enhancing imaging quality. The results confirm the feasibility of using NAMLs in complex optical systems requiring adaptive aberration control, making them suitable for integration into compact, high-resolution optical platforms.

Influence of technological parameters on the hot-pressed process of CaF2 optical ceramics

Nguyen Tuan Hieu, Tran Duc Long, Nguyen Dinh Quang — Mon, 25 Aug 2025 00:00:00 +0000

The paper uses the experimental planning method to study the influence of technological parameters on the hot pressing process of CaF₂ optical ceramics. The experimental planning model is applied to build the correlation equations between technological parameters, such as temperature, time, and pressure, on the quality index of the transmittance of optical ceramics. From there, the authors determine the optimal set of hot pressing technological parameters for the hot pressing process of CaF₂ optical ceramics. The research findings serve as an important basis for further studies on the hot-pressing process of various optical ceramics used in military optical devices.

Ballooncopter – A new prospective type of UAV

Tran Duy Duyen, Nguyen Duc Cuong, Mai Khanh, Nguyen Quoc Binh — Mon, 25 Aug 2025 00:00:00 +0000

It has been shown that an increasing demand for cheap and useful UAVs in recent years. At the same time, the requirement to reduce emissions (applying “green” technology) is also an increasingly urgent. The paper introduces a ballooncopter which combines the advantages of multi-rotor aircraft (drone) and balloon to meet the above requirements, and proposes solutions to overcome mechanical problems arising when coupling the balloon body and drone, citing examples of forest protection and some other application possibilities.