The practical application of Raman spectroscopy is often constrained by its low signal sensitivity, particularly for low-concentration liquid samples. This study introduces a straightforward platform that enhances Raman signals by physically concentrating analytes, providing an alternative to complex substrate fabrication and chemical treatments. We employed a femtosecond pulse laser to create functional micro-grid patterns on a silicon (Si) substrate. This laser process induces localized ablation and simultaneous oxidation, resulting in three-dimensional, hydrophilic microstructures of nonstoichiometric silicon oxide (SiO_2-x). These grid structures effectively confine aqueous sample droplets through a pinning effect, functioning as a microwell array that traps and concentrates suspended polystyrene (PS) particles. This physical concentration mechanism achieved a notable signal enhancement, with a maximum factor of 5.2 for PS particles, without the need for sample dehydration. This work presents a simple, cost-effective, and highly reproducible alternative to conventional SERS for analyzing low-concentration liquid samples, demonstrating strong potential for integration into microfluidic systems.

The design of the extrusion die significantly affects both the extrusion process and the quality of multi-lumen tubes. Traditional design methods that rely on trial and error tend to increase manufacturing time and costs while diminishing product quality. This study utilizes inverse extrusion simulation and optimization to design the extrusion die without the need for trial and error. The inverse extrusion simulation generates the die profile necessary to achieve the desired extrudate shape. Subsequently, direct extrusion simulations are conducted to predict the extrudate profile based on the derived die. The optimal volumetric flow rates of air within the lumens are also identified to ensure the extrudate meets the target profile. The results from the direct extrusion simulation, combined with optimization, confirm that the designed extrusion die can successfully produce the target profile. Using the derived die, the multi-lumen tube with the desired specifications is successfully extruded. This design and manufacturing approach enhances both the quality and productivity of multi-lumen tubes.

Military shelters contain various electronic devices that generate significant heat during operation due to their high power output. This heat buildup can degrade the performance of the equipment and shorten its operational lifespan. In high-temperature environments, overheating can lead to serious malfunctions in communication systems or information management platforms, jeopardizing the efficiency and reliability of military operations. Conversely, in low-temperature or high-humidity conditions, condensation may form inside the shelter, increasing the risk of physical damage to electronic components. Such damage can significantly compromise the reliability and durability of the equipment, raising the likelihood of system failure. This study proposes using various environmental control systems, including heating, ventilation, and air conditioning (HVAC) units and air ducts, to mitigate the adverse effects of temperature and humidity fluctuations within military shelters. To achieve this, thermal analysis models were utilized to evaluate and verify the performance of these systems. The analysis specifically examined the heat output of individual devices to determine if the proposed control systems could effectively maintain optimal operating temperatures within the shelter. The results of this study aim to provide a valuable foundation for designing environmental control systems that ensure thermal stability in military shelters.

Digital twin technologies in manufacturing have evolved into dynamic, data-synchronized systems that facilitate real-time monitoring and control. Given that machining involves closely interconnected multi-physics behaviors, the effectiveness of a digital twin largely relies on the accuracy and reliability of its underlying process models. This review systematically evaluates three primary paradigms for machining process modeling in digital twins: physics-based, data-driven, and hybrid approaches. Physics-based models provide interpretability and physical consistency but are hindered by high computational costs and limited adaptability to changing conditions. In contrast, data-driven models offer real-time capabilities and adaptive learning but face challenges related to data scarcity and black-box behavior. Hybrid modeling has emerged as the most promising approach, combining physical laws with machine learning through techniques such as parameter correction, physics-guided learning, and state-estimation-based intelligent control. Recent research demonstrates significant advancements in predictive performance, adaptability, and computational efficiency across various machining applications, underscoring the effectiveness of new process modeling strategies for digital twins. However, challenges remain, including multi-physics integration, model reduction for real-time deployment, and autonomous self-updating in data-limited scenarios. The review concludes that hybrid models present the most viable pathway to achieving high-fidelity, self-adaptive, and trustworthy digital twins for autonomous manufacturing.

This study examines the porosity behavior during the directed energy deposition (DED) of dissimilar metals S45C and H13. We analyzed the effects of deposition parameters, including laser power, feed rate, and powder characteristics, on pore formation, taking into account the unique properties of these metals. Our findings indicate that laser power is the primary factor influencing porosity. At a low power of 200 W, insufficient energy input, along with differences in thermal conductivity and chemical composition between S45C and H13, led to incomplete melting and lack-of-fusion, resulting in high porosity. As the laser power increased to 400-600 W, the melt pool stabilized, enhancing interfacial bonding and significantly reducing porosity. However, at an excessive power of 800 W, rapid melting and solidification of the powder caused gas entrapment and pore formation, which increased porosity, particularly due to the differing thermal conductivities of S45C and H13. Therefore, our results suggest that maintaining an adequate laser power of 400-600 W is essential for achieving a stable melt pool and minimizing porosity in the DED process for dissimilar S45C and H13 metals.

Cable chains are essential in the semiconductor industry for preventing the twisting or sagging of moving cables. They can be broadly categorized into two types based on their fastening methods, with rivet-based assembly being the most common. An alternative method utilizes integral locking features without rivets, which simplifies manufacturing and reduces production costs. However, integral cable chains are more susceptible to breakage during assembly, limiting their use in various industrial environments.This study introduces a structural design approach aimed at minimizing localized stress during assembly while ensuring the cable chain meets the required retention force. Design variables were selected from the modifiable features of the integral cable chain. Through sensitivity analysis, we identified key variables that significantly influence the retention force, which allowed us to reduce the number of design iterations. By employing finite element analysis and response surface methodology, we derived an optimal shape that achieved the target pull-out force and resulted in a 9.7% reduction in assembly stress compared to the original design.

The future mobility industry is increasingly utilizing advanced tools for cutting and machining lightweight parts to enhance the fuel efficiency of automotive engines. Machining companies are turning to polycrystalline diamond (PCD) tools to boost productivity in the production of these lightweight components. PCD tools provide exceptional machining performance and a long service life, making them ideal for high-mix, low-volume production, which often involves customized requirements for various materials. To further improve efficiency, this study explores the application of metal 3D printing technology in the manufacturing of PCD tools. This technology allows for the creation of PCD tools with superior cutting performance and wear resistance, tailored for high-speed machining of lightweight materials, including complex shapes. Thus, research into this area is essential. In this study, we manufactured boring tools by brazing PCD tips onto three different laminated structures created using Fused Deposition Modeling (FDM), a method within metal 3D printing technologies. We then evaluated the fabricated boring tools through comparative machining experiments against existing sintered PCD boring tools. The results indicated that the 3D-printed solid tools demonstrated no significant differences in machining accuracy or surface quality compared to the conventional tools.

The Split Hopkinson Pressure Bar (SHPB) experiment is commonly employed to assess the dynamic mechanical properties of materials under high strain-rate conditions (10²-10⁴ s-¹) through the propagation of elastic stress waves via pressure bars. The precision and dependability of SHPB measurements are heavily influenced by the alignment of the specimen with the bars. Misalignment can lead to flexural vibrations, causing waveform distortion and undermining the assumption of one-dimensional stress waves. While previous research has explored the impact of misalignment on waveform characteristics, pinpointing the specific sources of distortion from measured signals remains a challenge. This study introduces a machine learning-based classification method that extracts features from distorted SHPB waveforms to identify the type of misalignment. Incident wave signals under various misalignment scenarios were simulated using the commercial finite element software LS-DYNA, and the extracted features were utilized to create a training dataset. Several machine learning models, including XGBoost, were trained and evaluated, with XGBoost yielding the highest accuracy and F1-score. The trained model was then applied to experimentally measured distorted waveforms to validate its effectiveness. This proposed approach facilitates the automated diagnosis of distortion sources in SHPB data, reducing the need for manual interpretation and improving analysis efficiency.

This paper presents model-based hysteresis and cross-coupling compensators designed for precise control of a piezoelectric fast steering mirror (FSM). The hysteresis compensators are developed by inversely modeling the variation in the force constant relative to various excitation voltages, enabling the system to maintain linear response characteristics across a broad range of input amplitudes. The cross-coupling compensator is formulated by creating a decoupling matrix that cancels out coupling effects, generating signals of equal magnitude and opposite phase for each axis. The implementation of these compensators reduces the hysteresis band and magnitude uncertainty in the FSM dynamics by over 89.6% and 74.2%, respectively, while also significantly suppressing cross-coupling effects by more than 85.5%. Furthermore, the performance of the proposed compensators is validated in a closed-loop control system, demonstrating a notable reduction in cross-axis vibrations and improved tracking performance in response to step reference inputs and highfrequency sinusoidal trajectories.

The rising demand for robots in warehouses has highlighted the need for efficient multi-robot algorithms. In response, researchers have focused on Multi-Agent Path Finding (MAPF), which enables multiple agents to calculate conflict-free paths to their individual goals. However, the computation time of conflict-based MAPF algorithms significantly increases as the number of conflicts rises, a common challenge in warehouse environments with narrow passages or corridors. To tackle this issue, this study introduces a new type of conflict called “Overlap Conflict.” Overlap Conflicts occur when an agent stops, causing chain conflicts among subsequent agents traveling in the same direction. When an Overlap Conflict arises, the affected agents are dynamically merged into a single group, shifting the conflicts from an individual level to a group level. If the merged agents find themselves with unreachable goals, they are split back into individual agents to continue calculating paths to their respective destinations. This approach effectively reduces computation time in congested environments, particularly in narrow corridors where alternative routes exist.

We present an extrusion-based dispensing system designed for the planar patterning of tungsten ink through direct ink writing. This system achieves uniform ink deposition by precisely controlling the dispensing pressure and the motion of the substrate along predefined writing paths. To assess the impact of pressure on pattern geometry, we fabricated line patterns under various pressure conditions and analyzed their widths and thicknesses. To gain further control over pattern width, we employed an adjacent line overlapping strategy, where several lines, each approximately 200 μm wide, were written with partial overlap. We quantitatively verified the relationship between the number of adjacent lines and the resulting pattern width. This method was also adapted to create planar patterns with complex geometries, including variable widths, curved paths, and discontinuous features. The resulting patterns demonstrated uniform quality and precision. These findings confirm that our proposed system provides a versatile solution for fabricating planar conductive patterns with intricate geometries, suitable for applications in printed electronics and interconnects.

Balloon catheters are a key technology in medical devices, essential for minimally invasive procedures. This study quantitatively analyzes how the orientation characteristics of polymer tubes, influenced by extrusion conditions, affect the mechanical properties and compliance of the final balloon—where compliance refers to the change in diameter under external pressure. Nylon 12 tubes, with a target outer diameter of 1.2 mm and an inner diameter of 1.0 mm, were extruded under six different orientation conditions by varying the screw flow rate and puller speed. The tubes were processed under identical forming conditions, allowing for a consistent evaluation of their mechanical properties. As orientation increased, elongation decreased while yield strength increased, and these trends continued in the balloon, significantly influencing compliance. To quantitatively measure orientation, we introduced the dimensionless Deborah number. We established a curve-fitted experimental model that links extrusion conditions, polymer tube properties, and balloon compliance. This model allows for the prediction of balloon performance based on extrusion-stage parameters, providing a practical framework for process optimization. Overall, this study offers an effective quantitative indicator for forecasting balloon catheter performance based on extrusion conditions and supports the systematic design of medical balloon products.

All-solid-state batteries (ASSBs) utilizing non-flammable inorganic electrolytes are gaining significant attention due to safety concerns associated with conventional lithium-ion batteries. Among various oxide electrolytes, lithium lanthanum titanate (LLTO) demonstrates high ionic conductivity at room temperature but is prone to lithium loss at elevated sintering temperatures. In this study, we employed electrostatic spray deposition (ESD) at 250℃, followed by flash light sintering within milliseconds using a xenon lamp. This approach enabled the production of dense and highly crystalline LLTO thin films with minimal lithium evaporation. Scanning electron microscopy (SEM) analysis confirmed reduced porosity at 650V, while X-ray photoelectron spectroscopy (XPS) revealed stable lithium content. Additionally, X-ray diffraction (XRD) indicated the formation of a cubic perovskite structure that is beneficial for ionic transport. This rapid and scalable process shows promise for producing high-quality LLTO electrolytes, thereby enhancing the safety and performance of next-generation ASSBs.

This study evaluates the structural design and safety of the CanSat in launch environments. The CanSat serves as an educational replica satellite, allowing users to experience the design and operation of small satellites. To ensure stable operation during launch, the structural analysis and design must consider external forces, including vibration and acceleration loads. We determined the material properties for the structure and conducted modal and random vibration analyses, comparing the results with launch environment data from NASA, ECSS, Falcon 9, and Soyuz-2. Additionally, we performed an acceleration load analysis using actual data from CanSat launches during competitions. The modal analysis indicated that the first natural frequency was 65.34 Hz, which exceeds the required threshold. The random vibration and acceleration load analyses further confirmed the structural safety of the design. While the data from NASA and ECSS were conservatively set, reflecting higher vibration intensities, the Falcon 9 and Soyuz-2 launch vehicles provided relatively lower vibration environments due to differences in their designs. Overall, the results demonstrate that the CanSat's structural integrity is maintained under the conditions analyzed for Falcon 9 and Soyuz-2.

Fretting corrosion results from microscopic abrasion of connector contacts and is influenced by environmental conditions in automotive applications. This study designed and fabricated test equipment capable of evaluating fretting corrosion characteristics at low temperatures. A temperature–humidity environmental chamber was used, and a compact test jig box was created to fit inside it. The specimen was positioned outside the box and fully exposed to low temperatures, while the driving components were enclosed inside the box. To ensure their reliable operation, warm air was supplied using vortex tubes, maintaining the internal box temperature above 0oC even when chamber conditions reached −40℃. A hemispherical-tip jig was also produced to enable consistent specimen preparation. Experiments conducted at −40℃ used a constant current–resistance method to measure output signals. The system successfully captured accurate and stable resistance changes corresponding to displacement cycles. These findings indicate that the developed equipment provides stable low-temperature operation and reliable measurement performance. Therefore, the system is expected to support fretting corrosion characterization across a wide range of environments, including low-temperature, high-temperature, and temperature-cycling conditions.