Journal of Applied Science and Technology

RESEARCH AND DEVELOPMENT OF A TESTING SYSTEM FOR SCREW VACUUM PUMPS

Tuan Hieu-Nguyen — 2026-06-20

This study addresses the need for a systematic approach to evaluating the performance of vacuum pumps through the design of a dedicated experimental test system. The proposed system is developed to determine and measure key operating parameters of a vacuum pump under controlled conditions. Particular emphasis is placed on the relationship between vacuum pressure and the time required to achieve it, which serves as a critical indicator of pump efficiency. The design and implementation of this experimental setup constitute a
fundamental step toward subsequent investigations aimed at optimizing vacuum pump performance.

EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF WELDING PARAMETERS ON WELD GEOMETRY AND MICROSTRUCTURE OF GMAW BUTT-WELDED PIPE JOINTS

Thân Văn Thế — 2026-04-16

This paper investigates the influence of welding current, travel speed, and arc voltage on the weld geometry of S235JRH steel butt-welded pipe joints with GM-70S filler wire. The experimental plan was arranged according to a Taguchi L9 orthogonal array to reduce the number of trials while preserving the ability to evaluate the main effects of the welding parameters. The results show that increasing the welding current from 90 A to 100 A increases the thermal energy supplied to the joint, resulting in an increase in welding width from 5.8 mm to 7.8 mm and penetration depth from 1.7 mm to 3.2 mm. In addition, increasing the travel speed from 4.6 mm/s to 5.0 mm/s reduced the weld reinforcement height from 1.7 mm to 1.2 mm.
Arc voltage also significantly affected weld formation, particularly weld width. Under welding condition M07 (100 A, 4.6 mm/s, 20 V), the weld exhibited relatively large width and reinforcement height, reaching 7.8 mm and 1.8 mm, respectively. Microstructural analysis showed that the weld metal mainly consisted of ferrite and bainite, satisfying the mechanical property requirements of the pipe butt-welded joint.

EVALUATING THE EFFECT OF INTERLINING TYPE ON THE SHRINKAGE AND ADHESION STRENGTH OF INTERLINING – PRESSED FABRIC SAMPLES BEFORE AND AFTER WASHING, USED IN WOMEN'S VESTS

Giần Thị Thu Hường — 2026-06-05

Choosing the right interfacing material for the fabric directly affects the quality of the interfacing and the quality of the finished garment. This study investigates the influence of the interfacing material structure on the shrinkage and adhesion of three types of interfacing – non-woven, woven, and knitted – after interfacing and after washing, using fabric samples for making women's vests. The results show that with a woven interfacing base combined with a woven fabric sample, the shrinkage in both the vertical and horizontal directions of the sample is lowest and particularly best in the direction of the interfacing. Simultaneously, the adhesion strength of the woven interfacing is also better than that of the non-woven
interfacing. These research results provide a scientific basis for selecting the appropriate interfacing for woven fabrics in garment production.

PATTERN REPEAT DETERMINATION AND MARKER MAKING FOR STRIPED AND PLAID FABRICS IN INDUSTRIAL APPAREL MANUFACTURING

Nguyễn Thị Hồng Khanh — 2026-05-05

In industrial garment manufacturing, marker making plays a crucial role in determining pattern layout, material consumption, and the quality of semi-finished products prepared for mass cutting and sewing. Marker making for striped fabrics is particularly challenging due to strict requirements for stripe alignment and matching accuracy. This study investigates and develops a technical method for determining striped fabric pattern repeat and corresponding marker making strategies to improve fabric utilization efficiency and product quality. Field surveys were conducted at three large-scale garment manufacturing enterprises in Northern Vietnam, providing practical data for analysis. Based on these surveys, a combined method for pattern repeat determination and marker making was developed and adapted to the characteristics of six common types of striped and plaid fabrics. Experimental application to an actual production order demonstrates that the proposed method reduces major defects related to stripe matching and alignment by 6.1%, decreases stripe deviation, and lowers the rework rate by 4.5% during production. The results confirm the effectiveness and feasibility of the proposed approach under industrial manufacturing conditions. This research has strong practical significance, contributing to the improvement and standardization of marker making processes for striped fabrics, and offers a solution that can be directly applied in industrial garment manufacturing enterprises.

RESEARCH AND MANUFACTURE BUTTONHOLDER AND BUTTON ATTACHMENT FOR SHIRTS, SUPPORTING PRACTICAL TRAINING IN SEWING TECHNOLOGY AT HUNG YEN UNIVERSITY OF TECHNICAL EDUCATION

Nguyễn Chí Công — 2026-06-05

This research focuses on developing two jig sets for the buttonhole and button-attaching stages of shirt sewing on Juki LBH-1790S and Juki LK-1903ASS machines, aiming to improve the efficiency of practical sewing technology training. The jig sets are designed based on a positioning-guiding-fixing model for semi finished products, ensuring precise position control, stable operation, and repeatability of the processing. Pedagogical experiments showed that the time required for the two stages was reduced from 142 seconds to 97 seconds per product (a 31.7% reduction), while completely eliminating intermediate activities such as manual marking and adjustment. As a result, the uniformity of finished products is significantly improved, and the training process is standardized according to the requirements of industrial product standards. The research results confirm the effectiveness of the jigs and fixtures system in improving training quality and its potential for practical implementation in training institutions as well as small and medium-sized enterprises.

EVALUATION OF YARN QUALITY ON MACH CONER 7-II, LINK CONER 7V-II, AND MURATA 21C WINDING MACHINES

Hoàng Thanh Thảo — 2026-06-15

This paper presents the experimental results evaluating yarn count, count unevenness, absolute breaking strength, specific strength, strength unevenness, breaking elongation, twist, twist unevenness, and appearance quality indicators of a high-quality yarn produced in Vietnam after winding on three widely used automatic winding machines, namely Mach Coner 7-II, Link Coner 7V-II, and Murata 21C. The study aims to assess yarn quality parameters after winding on different winding machines and to compare the results with standard requirements. The research provides a scientific basis for selecting suitable winding machines in order to improve production efficiency and enhance the quality of wound yarn products.

NUMERICAL SIMULATION OF A GASOLINE ENGINE EXHAUST AFTER-TREATMENT SYSTEM IN AVL CRUISE

Trần Anh Dương — 2026-04-12

This study develops a numerical simulation model to investigate the operating characteristics of the exhaust after-treatment system in a gasoline engine equipped with a three-way catalytic converter (TWC). The model allows flexible variation of input conditions and is applied to analyze the effects of engine temperature and the air–fuel equivalence ratio (λ), while the exhaust mass flow rate is kept constant at 300 kg/h, corresponding to the typical operating condition of a Toyota Vios. The simulation results show that as the engine temperature increases from 30 to 100 °C, the exhaust gas temperature rises accordingly; however, the post-TWC temperature drop remains within only 0.2–6.6 °C, indicating the limited heat-transfer characteristics of the system. The O₂ concentration downstream of the catalyst decreases significantly in the rich mixture region (λ = 0.8–0.9) due to higher oxidation reaction rates, while exhibiting minimal variation at λ ≥ 1.0. The conversion efficiencies of CO and NO increase with temperature and reach their maximum values at λ ≈ 0.9. These simulation results are mostly qualitative, illustrating the characteristic operating trends of TWC systems, and can serve as a preliminary foundation for future studies on optimizing emission control and calibrating air–fuel mixture strategies in gasoline engines.

UNIVERSITY STUDENTS’ EVALUATIONS OF ONLINE AND IN-STORE FASHION SHOPPING AND THEIR CHANNEL PREFERENCE IN NORTHERN VIETNAM

Trần Xuân Uyên — 2026-05-26

In fashion retail, the growth of digital commerce has expanded students’ use of online channels without displacing the role of physical stores. For this product category, channel choice is shaped not only by price and ease of purchase, but also by the wish to inspect garments directly and reduce uncertainty before committing to a purchase. This study compares how university students in Northern Vietnam evaluate online versus in-store fashion shopping and identifies factors associated with channel preference. The analysis is based on 185 valid survey responses and combines paired comparisons, binary logistic regression, and PLS-SEM. The results indicate that online shopping receives higher evaluations on most perceptual dimensions, especially shopping experience, perceived product quality, and social influence. Even so, convenience associated with in-store shopping still affects the final choice. These findings suggest that favorable perceptions of digital shopping do not automatically translate into exclusive online preference, and that fashion retailers should coordinate digital reach with the assurance provided by physical stores.

HIGHSPEED DELTA ROBOT SORTING SYSTEM WITH INTEGRATED COMPUTER VISION: DESIGN AND EXPERIMENTAL STUDY

Nguyễn Thị Vân — 2026-06-10

The paper presents the design and implementation of a Delta robot system integrated with computer vision for color-based sorting of multi-colored products on a moving conveyor. To optimize cost and enhance localization, the study embeds the 3-DOF translational inverse kinematics algorithm directly into a standard S7-1200 PLC controller instead of using expensive dedicated motion controllers. The computer vision system is developed in Python and utilizes the HSV color space for real-time object recognition, environmental noise suppression, and object centroid detection. To eliminate geometric discrepancies between the camera and the mechanical coordinate system, an automatic calibration algorithm based
on a 2D affine transformation matrix combined with a second-order polynomial interpolation function is implemented, effectively compensating for conveyor tilt and Z-axis height errors with an average error of ±0.45 mm. Communication between the image-processing computer and the PLC is optimized via a handshaking mechanism over TCP/IP (Snap7 library), achieving a communication delay of only 4.2 ms and a total closed-loop response time of 38.5 ms. Experimental results demonstrate that the system operates stably with a PLC scan cycle from 1.8 ms to 2.2 ms, accurately tracking workpieces at a maximum conveyor speed of 350 mm/s, and achieving an actual sorting throughput of 60 products per minute.

MASSERA-TYPE THEOREM TO A CLASS OF SEMI-LINEAR DIFFERENTIAL EQUATIONS

Nguyen Thi Loan — 2026-06-18

In the present work, by applying a Massera-type theorem, we derive sufficient conditions for the existence and uniqueness of periodic solutions to a class of partial functional differential equations of the form

here the operator A(t): E ⊇ D(A) → E is τ-periodic and possibly unbounded; the operator Γ(·, x(·)) takes values in a Banach space E, the function α takes values in the Banach space D(A), and are τ-periodic.

INVESTIGATION OF THE ADSORPTION PERFORMANCE OF MnO₂ PREPARED BY THE CO-PRECIPITATION METHOD

Chu Thị Thúy Hằng — 2026-06-26

Manganese dioxide (MnO₂) prepared via a co-precipitation route was explored as an adsorbent for the removal of Amido Black 10B from aqueous media. The adsorption performance of the material was assessed under different operating conditions, with emphasis on solution pH, initial dye concentration, and adsorbent reusability. Surface morphology and crystalline structure were examined using field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), respectively. The point of zero charge (pHpzc) of MnO₂ was determined to be approximately 5.8, indicating that the surface charge characteristics of the material are strongly influenced by the surrounding pH. Under the investigated conditions, the highest dye removal efficiency approached 95% at pH 2, while the adsorption capacity reached approximately 370.63 mg.g⁻¹. In addition, the adsorbent retained a substantial fraction of its original performance after repeated use, maintaining a removal efficiency above 70% following three consecutive adsorption desorption cycles. These findings suggest that co-precipitated MnO₂ represents a promising candidate for the treatment of dye-contaminated wastewater, particularly streams containing anionic colorants.

SENSITIVITY ANALYSIS OF OFFSHORE WIND PRODUCTION COST WITH RESPECT TO WIND SPEED AND TRANSMISSION DISTANCE

Tran Thi Ngoat — 2026-06-15

This paper presents a nonlinear mathematical model to analyze the effect of wind velocity on the cost of electricity generation (LPC) in an offshore wind power project with the research scenario of the La Gan wind power project in Vietnam. Using the GAMS modeling tool and input data from the pre-feasibility study report of the La Gan project, the study carried out sensitivity analysis for many scenarios with average wind velocities ranging from 5 m/s to 9 m/s, transmission distances ranging from 30-90km. The LPC model is established based on the components of investment cost (CT), operation and maintenance (CM), and annual power output, in which the power output is modeled in the cube of velocity. The results show that the transmission distance has a significant sensitivity to the LPC at a low wind speed of 5 m/s and a low sensitivity at a speed of 9 m/s. This confirms that the location of the offshore wind power project should be selected based on wind speed to ensure project feasibility.

STUDY ON THE INFLUENCE OF CUTTING FACTORS ON THE CHIP SHRINKAGE COEFFICIENT IN THE TURNING OF AA6061 ALUMINUM ALLOY

Hoa-Thi Pham — 2026-06-16

This study investigates the influence of cutting parameters on the chip shrinkage coefficient (K) during the turning of AA6061 aluminum alloy using a Taguchi experimental design. Four machining parameters— tool nose radius (r), cutting speed (V), feed rate (f), and depth of cut (t)—were evaluated at three levels, and their effects were analyzed through signal-to-noise (S/N) ratio, analysis of means, and interaction plots. The results indicate that feed rate is the dominant factor affecting K (chip shrinkage coefficient), followed by depth of cut, whereas tool nose radius and cutting speed have relatively minor influences. A significant interaction between feed rate and depth of cut demonstrates that chip shrinkage is primarily governed by uncut chip geometry, which intensifies plastic deformation and shear in the primary deformation zone. The optimum cutting conditions for minimizing K were identified as r = 0.4 mm, V = 150 m/min, f = 0.08 mm/rev, and t = 0.5 mm. The novelty of this work lies in providing a systematic quantitative assessment of both the individual and interactive effects of machining parameters on the chip shrinkage coefficient, revealing the dominant role of uncut chip geometry in chip formation. These findings offer new insights into chip deformation mechanisms and provide practical guidelines for optimizing the turning performance of AA6061 aluminum alloy.

INFLUENCE OF DEPOSITION RATE ON THE FORMATION AND INTERFACE STRUCTURE OF NiCo THIN FILMS ON Ni

Van-Khoe Pham — 2026-06-25

Molecular dynamics simulations were performed to investigate the effect of deposition rate on the growth of Ni₅₀Co₅₀ thin films on a Ni(001) substrate. Deposition rates from 5 to 25 atoms/ps were examined at 300 K with an incident energy of 2 eV. Higher deposition rates increased surface roughness, structural disorder, and interfacial atomic mixing, whereas lower rates promoted smoother films and sharper interfaces. These findings provide atomistic insights into thin-film growth and guidance for optimizing NiCo coating deposition.

RESEARCH ON IMPROVING ERROR COMPENSATION ALGORITHMS IN BALL SCREWS

Trần Đức Toàn — 2026-06-30

Ballscrew drive is a mechanical mechanism that is said to have a relative motion relationship between the rotation angle of the screw shaft and the displacement of the nut - this relationship is linear, making them a natural choice for designing high-precision machinery and CNC machines due to their ease of calculation and control. However, in practice, many objective factors clearly cause inaccuracies in measurement results compared to calculations – leading to errors in machine design and manufacturing – making it difficult to master the design and production of automated and high-precision industrial machinery/equipment using ballscrews drive. Based on in-depth researchs on factors affecting the operating error of ballscrews, the author proposes supplementing and modifying a program to calculate and control error compensation for the control system, contributing to improved accuracy.

ANALYSIS OF METAL ADDITIVE MANUFACTURING TECHNOLOGY TRENDS AND PROPOSED DESIGN FOR A LABORATORY-SCALE SLM 3D PRINTING SYSTEM IN VIETNAM

Nguyễn Thành Huân — 2026-06-16

Metal Additive Manufacturing (Metal AM) technology is rapidly developing with many unique ideas. Among them, the method of using lasers or electron beams to melt a layer of metal powder (Powder Bed Fusion – PBF) is widely applied due to the high precision of the resulting product and the superior mechanical properties compared to other processing methods. This paper analyzes research on 3D printing technology of metal materials worldwide, examines its practical application in domestic research and training, and proposes a design model for a laboratory-scale Selective Laser Melting (SLM) 3D printing system that is cost-effective, safe, and suitable for localization. The research shows that designing and manufacturing a small-scale SLM system is feasible and highly valuable for training, materials research, and mechanical processing at universities, academies, and research institutes in Vietnam.

APPLYING MODEL PREDICTIVE CONTROL FOR QUADROTOR STATE STABILIZATION IN THE PRESENCE OF DYNAMIC OBSTACLES

Nguyễn Văn Minh — 2026-06-26

This paper proposes a Nonlinear Model Predictive Control (NMPC) approach applied to a quadrotor to simultaneously maintain position and avoid 3D dynamic obstacles. Based on a 6-degree-of-freedom (6-DOF) dynamic model, the NMPC controller continuously solves a nonlinear programming problem subject to constraints regarding a safe spatial region—incorporating a buffer zone to compensate for mechanical inertia—and actuator capacity limits. Numerical simulations utilizing the CasADi/IPOPT solver were conducted to evaluate the system under two scenarios: abrupt avoidance (prioritizing position tracking) and smooth avoidance (optimizing control signals). The results demonstrate that the algorithm not only successfully prevents collisions with continuously moving obstacles but also offers flexibility in fine-tuning flight behavior through the prediction horizon and weighting matrices, thereby satisfying diverse practical operational requirements.