NKRAFA JOURNAL OF SCIENCE AND TECHNOLOGY

Overview of Induction Hot Wire Preheating Techniques in GTAW and GMAW

Sun, 22 Mar 2026 00:00:00 +0700

Preheating filler wire before welding using induction heating coils is a technique that has been developed and applied to various welding processes, such as Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW), to improve the melting efficiency of the filler wire. This is achieved by reducing the temperature difference between the filler wire and the base material, resulting in a higher deposition rate without increasing the overall heat input to the weld. In addition, this technique benefits the mechanical properties of the weld, such as hardness, toughness, and impact resistance. It also helps to reduce the risk of porosity, as preheating assists in removing moisture on the surface of the filler wire prior to welding. Moreover, it reduces the heat input into the workpiece, leading to finer grain structures and increased hardness in the weld zone. This article presents a study on the effects of preheating filler wire using induction heating coils on deposition rate, microstructure, mechanical properties, and the influence of electromagnetic fields induced by the heating coils on arc stability and weld quality

Study of High Entropy Alloy Cladding Using Gas Tungsten Arc Cladding

Sun, 22 Mar 2026 00:00:00 +0700

High-entropy alloys (HEAs) are materials that have attracted much attention due to their outstanding properties, such as mechanical strength, heat resistance, and wear resistance. This paper reviews literature on the preparation of high entropy alloy powders using the high-energy ball milling process for application in the gas tungsten arc cladding process to examine the structure and corrosion resistance of the resulting cladded layers. It is found that the process distributes various elements uniformly, resulting in a strong dendritic structure. After cladding, the material exhibits increased hardness and improved corrosion resistance, as some elements have the ability to form a protective, corrosion-resistant film. Therefore, high-entropy alloys have significant potential for the development of advanced engineering materials.

A Study on Reducing Transportation Costs: A Case Study of ABC Concrete Panel and Construction Materials Manufacturing Company

Ratchadakorn Poohoi, Chayachot Chaleeprom — Tue, 23 Dec 2025 00:00:00 +0700

In 2025, the competition in transportation to meet consumer demand has intensified, and high transportation costs play a significant role in distributing products to the market. This research aims to study methods for reducing transportation costs through a case study of the ABC concrete panel and construction materials manufacturing company. The study began with an analysis of the current situation to determine the true proportion of transportation costs. Subsequently, a Full Truckload (FTL) flat-rate costing model was applied to reduce costs. The results of the study reveal that the application of the FTL method led to a significant cost reduction, resulting in savings of 1,644,379 THB, or an 18.93% decrease compared with the distance-and-fuel-based costing method. Furthermore, the average cost of the FTL approach was found to be significantly lower than that of the distance-based model (p-value < .05). The Full Truckload method can be applied to other industries to optimize transportation efficiency and minimize total transportation costs.

Clustering and Analysis of Circular Economy Indicators by Economic Sector and Waste Type Using Machine Learning

Noppadol Panchan — Mon, 05 Jan 2026 00:00:00 +0700

This study aims to analyze and classify patterns of circular economy systems across different economic sectors. It integrates secondary data analysis with machine learning techniques. To date, no prior study has systematically linked circular economy (CE) indicators with both economic sectors and types of waste. The research utilizes secondary data from 877 research articles indexed in the Scopus database published between 2010 and 2024. Six key CE indicators are examined, including the material circularity indicator (MCI), waste hierarchy index (WHI), recycling rate (RR), reuse potential index (RPI), resource efficiency indicator (REI), and circular material use rate (CMUR). Principal Component Analysis (PCA) and K-Means Clustering are applied to identify distinct patterns within the dataset. The findings reveal that the agriculture and food industries are strongly represented in the "circular-dominant" cluster, while the construction and metallurgy sectors are primarily associated with the "linear-dominant" cluster, which exhibits limitations in circular performance. However, the analysis faced certain limitations, including data imbalance across sectors and inconsistencies in indicator definitions. These insights can support the design of sector-specific circular economy policies and contribute to the development of recommendation systems for selecting appropriate indicators based on waste types and industrial contexts. The results serve as a foundation for accelerating the practical transition toward a circular economy.

Reducing Electrical-Test Cycle Time for Electronic Component

Chayathach Phuaksaman — Mon, 05 Jan 2026 00:00:00 +0700

This research aims to lower the overall manufacturing time of a specific integrated-circuit (IC) product by shortening the electrical-test stage, which has a direct impact on the total cost. The existing testing procedure required an average of 11.53 s to process 480 units and generated an aggregate production cost of THB 1,863,655 for fiscal years 2023–2024. A root-cause analysis using a fishbone diagram and a time study on the testing procedure found that the long test time was mainly due to the graphics processing and display on the screen needed for the operator, particularly the Yield window that showed bar-chart graphics. To address these inefficiencies, it is crucial to streamline the graphics processing or consider alternative display methods that minimize delays. Implementing these changes could significantly reduce the testing time and ultimately lead to a decrease in overall production costs. The improvement strategy involved closing unnecessary display windows and replacing the bar-chart yield window with a text-based output. This modification reduced individual machine time for that step from 3.83 s to 0.58 s. The comprehensive post-improvement test results, which utilized a design of experiment, confirmed that the total electrical-test cycle time decreased to 7.96 seconds, indicating a 31% reduction. Correspondingly, the projected production cost for 2023–2024 decreased by THB 852,990, or 46%. The approach is readily transferable to other IC products and offers a practical pathway for organization-wide efficiency gains and cost reduction.

Optimal Order Quantity for Football Jersey Inventory Under Normal and Seasonal Demand Using FlexSim

Anan Butrat, Chutikarn Suppatvech — Mon, 05 Jan 2026 00:00:00 +0700

Effective inventory management is critical for small to medium-sized (SMEs) retail businesses as they are usually facing demand fluctuations, especially for seasonal or promotional items. A case study of a football jersey retail shop in Pathum Thani has also experienced such a challenge, where they have relatively stable demand in normal months and fluctuating demand during football competition months. The shop typically orders a fixed quantity of 300 units during the normal period and 600 units during the seasonal period. However, this order strategy frequently leads to stockouts, resulting in lost sales opportunities and dissatisfied customers. Accordingly, the purpose of this study is to optimize and propose the order quantity strategy that balances stock levels. This study employs FlexSim, a discrete-event simulation software, to analyze and evaluate 14 scenarios of different order quantity strategies, testing different possible combinations of normal and seasonal order quantity values. The results show that Scenario 14 with a normal order quantity of 550 units and a seasonal order quantity of 950 units provided the optimal order quantity with 99.87% Releasing, 0.13% Empty, and no remaining inventory. Based on the results, this order quantity strategy minimizes stockouts while preventing excess stock accumulation, making it the most optimized order policy among the other 13 scenarios. The findings also highlight the importance of dynamic inventory control in optimizing inventory replenishment, where discrete-event simulation software (i.e., FlexSim) can be utilized by the SMEs in the retail industry in fine-tuning order quantity values corresponding to demand fluctuations. Hence, retail businesses can improve customer satisfaction through enhancing inventory efficiency.

A Saving Algorithm Approach to Flight Path Management for Unmanned Aerial Vehicles

Fri, 30 Jan 2026 00:00:00 +0700

This study investigates the optimization of unmanned aerial vehicles (UAVs) flight routes for transporting documents and books within the Navaminda Kasatriyadhiraj Royal Air Force Academy. A simulation was developed to reflect potential real-world UAV delivery operations, integrating
air traffic management principles to improve resource utilization and efficiency. A heuristic approach, specifically the Savings Algorithm, was applied to design optimal flight paths with the objective of minimizing total travel distance. Seven designated locations were identified as both pickup and drop-off points, subject to legal constraints. Route construction and savings calculations were performed using the Savings Algorithm in combination with Microsoft Excel. The results indicated that, when Node 1 was set as the starting point, the most efficient routes were Route 1 (1-8-9-7-4-3-1) and Route 2 (1-2-1). The greatest pairwise saving was observed between Node 8 and Node 9 (682.23 meters). By applying air traffic management concepts, the resulting flight patterns demonstrated improved efficiency, shorter travel distances, and faster delivery times. These findings suggest that the Royal Thai Air Force could adopt this routing framework as a practical guideline for document distribution within the organization, as well as adapt it to broader mission-related applications in the future.

Removal of Periodic Noise in Digital Images Using an Improved Notch Filter

Nalinnipa Arthan, Chaiyaporn Panyindee — Mon, 09 Feb 2026 00:00:00 +0700

Periodic Noise Removal in digital images is an important process that affects image quality. This research proposes the use of an improved Notch Filter combined with High Pass Filtering in geometric shapes, namely circles, triangles, squares, pentagons, and four-pointed stars, to improve the efficiency of Periodic Noise Removal. Standard images Lena.tif, Baboon.tif, and Jet.tiff with diagonal noise were used to evaluate performance. Two metrics were applied: Mean Squared Error (MSE) and Peak Signal-to-Noise Ratio (PSNR). The results indicated that for Lena.tif, the pentagon and four-pointed star increased PSNR by 5.12 dB and 5.11 dB, respectively, compared to the original Notch Filter, while circle, square, and triangle increased PSNR by 4.68-4.88 dB. For Baboon.tif, the original Notch Filter yielded the best performance; all geometric shapes decreased PSNR by 0.94-1.39 dB, indicating that the image content and noise pattern did not align with these shapes. For Jet.tiff, the pentagon increased PSNR by more than 5 dB. This study presented a new approach to frequency-domain filter design to effectively reduce periodic noise while preserving digital image quality.

Critical Frequency and Peak Height Variations of the F2 Ionospheric Layer in the Near-Equatorial Region During Low-Solar Activity

Patapong Panpiboon, Saharat Sathipchan — Mon, 23 Feb 2026 00:00:00 +0700

This study investigated the variability of the critical frequency (foF2) and F2 layer peak height (hmF2) in the equatorial magnetic region during low solar activity, utilizing 35,749 data points from the BVJ03 Ionosonde station throughout 2018. Results revealed foF2 median values of 6.85 MHz (IQR: 4.30-8.68 MHz) and hmF2 median values of 282.9 km (IQR: 251.1-316.7 km). Monthly variations exhibited equinox anomaly characteristics, with foF2 declining from 8-9 MHz (January-April) to 5-6 MHz (July-August), while hmF2 demonstrated opposite trends. Seasonal analysis showed maximum foF2 values during autumn (~11 MHz). Diurnal variations indicated minimum foF2 values before dawn (2-3 MHz) and maximum values during afternoon (13:00-15:00 LT), while hmF2 exhibited minimum values in the morning (220-250 km) and maximum values in the evening (320-350 km). Mann-Whitney U tests revealed statistically significant differences, with daytime foF2 (8.16 MHz) nearly doubling nighttime values (4.35 MHz), whereas nighttime hmF2 (291.80 km) slightly exceeded daytime values (275.70 km). Comparison with IRI-2020 models indicated systematic overestimation of hmF2, particularly during daytime hours (RMSE = 52.84 km). This research confirmed that foF2 was primarily influenced by solar radiation, resulting in pronounced day-night variations, while hmF2 was additionally affected by atmospheric dynamics. These findings enhanced understanding of low-latitude ionospheric behavior and can contribute to improving ionospheric parameter prediction models.

Waste Reduction of Press Load Testing in Steering Shaft Spline Production Process

Thanchuda Phannikul, Juthamas Daungjai — Sat, 28 Feb 2026 00:00:00 +0700

The automotive parts industry has continued to grow steadily over the past several years. Quality control of each component is of utmost importance, as it directly affects driver safety. The case study company, a manufacturer of steering column components, has recently faced quality-related defects during product testing. To address this issue, the research team applied various 7 QC Tools to identify root causes and develop corrective measures. The investigation began with the use of a Pareto chart to compare monthly production defect data, which revealed that the most defect was press load testing, where values frequently exceeded the customer-specified limit of 30 kN. A fishbone diagram (Ishikawa) based on the 4M principle was then used to analyze potential causes. The findings indicated that the main problems were the lack of machine adjustments and the wearing of the jig. As an initial corrective measure, the team installed shim plates (support fixtures) on both sides of the machine to stabilize the setup. Subsequent process monitoring using scatter diagrams and control charts showed that the press load values improved and remained within the customer’s specified range. Additionally, calculations of the process performance indices (P_p and P_pk) after the improvement showed better values, indicating reduced variation in press load measurements. Overall, the improvement reduced the defect rate related to excessive press load from 0.67% to an average of just 0.03% per month, representing a 95.52% reduction. The associated defect cost dropped significantly, from 7,635 THB to just 123 THB per month. Going forward, it is recommended to establish a systematic jig maintenance and machine calibration plan to prevent the recurrence of similar issues and to address other high-cost defects in subsequent phases.

Prediction of Sediment Accumulation Tendency During Heavy Rainfall in Khao Makok Area Using the HEC-RAS Model

Tue, 17 Mar 2026 00:00:00 +0700

The construction of buildings and structures in water flow areas caused sediment accumulation that obstructed waterways, leading to flash flooding problems in downstream areas during heavy rainfall exceeding normal levels. This research used the HEC-RAS hydraulic model to simulate water flow conditions during rainfall intensity of 31.4 millimeters per hour for 3 hours, as this rainfall intensity can cause flooding based on 20-year recorded rainfall statistics in the Khao Makok area, which was the location of the Navaminda Kasatriyadhiraj Royal Thai Air Force Academy. The water intake points from Khao Makok are spaced 250-300 meters apart. The simulation results revealed sediment accumulation from surrounding areas and flood risk. The model showed that water flowing through natural channels had higher velocity than surrounding areas, flowing into the Naval Academy area at approximately 1 m/s while carrying sediment along the natural waterway. In the western drainage area, sediment movement and accumulation occurred, while in the southern area, sediment accumulated in nearby areas before reaching the drainage system. This simulation study aimed to lead to the design of efficient drainage systems and sediment management in the future. The goal was to reduce risks from flooding, erosion, and soil accumulation, as well as to develop infrastructure for stable and sustainable water intake and drainage planning.

Evaluation of Engineering Properties of Recycled Asphalt Concrete Mixtures Containing 100% Original Asphalt Concrete Using Three Types of Asphalt Recycling Agent

Kamonwin Prasomsri, Nirachorn Nokkaew — Wed, 18 Mar 2026 00:00:00 +0700

This study investigated the laboratory engineering properties of 100 percent reclaimed asphalt pavement (RAP) mixtures, modified with three types of asphalt recycling agent. The RAP contained asphalt cement grade AC 60–70 as the original binder, with a residual RAP binder content of 4.50% by aggregate weight, equivalent to 54 grams. The recycled asphalt concrete specimens were prepared using the Marshall method and divided into four groups: Group 1 RAP without asphalt recycling agent (R), Group 2 RAP with AC 80–100 (RAC), Group 3 RAP with RA5 (RRA) and Group 4 RAP with PET (RPET). The asphalt recycling agent was added at proportions of 5.6, 11.1 and 16.7 % by weight of the residual RAP binder, using the dry mixing method. The engineering properties tested included density, stability, flow, indirect tensile strength, stiffness modulus, rutting resistance, and fatigue cracking resistance. The test results showed that, compared with Group 1 (R), the specimens in Groups 2 (RAC), 3 (RRA), and 4 (RPET) exhibited increased indirect tensile strength and stiffness modulus at 5.6% asphalt recycling agent content, but decreased values at 11.1% and 16.7%. An exception was found in Group 3, where at test temperatures of 30 degrees Celsius and 40 degrees Celsius, the stiffness modulus decreased at 5.6% RA5 content and continued to decrease with higher RA5 contents. Flow values and fatigue cracking resistance increased with the addition of asphalt recycling agent, whereas stability decreased as asphalt recycling agent content increased. For density and rutting resistance, Groups 2 (RAC) and 3 (RRA) showed increasing values with higher AC 80–100 and RA5 contents, while Group 4 (RPET) showed an initial increase followed by a decrease as PET content increased. In conclusion, the specimens in Group 2 with 5.6% AC 80–100 exhibited the most suitable combination of indirect tensile strength, stiffness modulus, and rutting resistance for pavement performance under Thai environmental conditions.