With the wide application of portable wearable devices, a variety of electronic energy storage devices, including microsupercapacitors (MSCs), have attracted wide attention. Laser-induced graphene (LIG) is widely used as electrode material for MSCs because of its large porosity and specific surface area. To further improve the performance of MSCs, it is an effective way to increase the specific surface area and the number of internal active sites of laser-induced graphene electrode materials. In this paper, N-doped polyimide/polyvinyl alcohol (PVA) as precursor was used to achieve in situ doping of nitrogen atoms in laser-induced graphene by laser irradiation. Through the addition of N atoms, nitrogen-doped laser-induced threedimensional porous graphene (N-LIG) exhibits large specific surface area, many active sites, and good wettability all of which are favorable conditions for enhancing the capacitive properties of laser-induced graphene. After assembly with PVA/H2SO4 as gel electrolyte, the high surface capacitance of the MSC device with N-LIG as electrode material is 16.57 mF cm− 2 at the scanning rate of 5 mV s− 1, which is much higher than the 2.89 mF cm− 2 of the MSC device with LIG as electrode material. In addition, MSC devices with N-LIG as electrode materials have shown excellent cyclic stability and flexibility in practical tests, so they have a high application prospect in the field of flexible wearable microelectronics.

세계적인 환경 규제로 인해 마그네슘 합금과 같은 경량 소재에 대한 수요가 증가하고 있으며, 마그네슘 합금 소재의 다양한 산업계 적용을 위한 용접 및 접합 방식에 대한 연구도 지속적으로 수행되고 있다. 앞선 Part I 연구에서는 마그네슘 합금에 대한 파이버 레이저 Bead on Plate(BOP) 실험을 수행하여 맞대기 용접 조건의 확보를 위한 기초 연구를 수행하였으며, 본 연구에서는 Part I의 기초 BOP 실험에서 도출된 적합한 레이저 출력과 용접 속도를 바탕으로 두께 3mm의 AZ31B 마그네슘 합금에 대해 맞대기 용접을 시행하였고, 인장시험 및 경도시험을 수행한 후 기계 물성 데이터를 분석하였다. 분석 결과 레이저 출력 2.0 kW, 50 mm/s (Heat input)의 조건에서 항복강도 151.5 MPa, 인장강도 224.1 Mpa으로 우수한 인장, 항복강도를 얻을 수 있었다.

In this study, laser-induced graphene oxide (LIGO) was synthesized through a facile liquid-based process involving the introduction of deionized (DI) water onto polyimide (PI) film and subsequent direct laser irradiation using a CO2 laser (λ = 10.6 μm). The synthesized LIGO was then evaluated as a sensing material for monitoring changes in humidity levels. The synthesis conditions were optimized by precisely controlling the laser scribing speed, leading to the synthesis of LIGO with different structural characteristics and varying oxygen contents. The increased number of oxygen-containing functional groups contributed to the hydrophilic properties of LIGO, resulting in a superior humidity sensing capabilities compared with laser-induced graphene (LIG). The LIGO-based sensors outperformed LIG-based sensors, demonstrating approximately tenfold higher sensing responsivity when detecting changes at each humidity level, along with 1.25 to 1.75 times faster response/recovery times, making LIGO-based sensors more promising for humidity-monitoring applications. This study demonstrated laser ablation in a renewable and natural precursor as an eco-friendly and energy-efficient approach to directly synthesize LIGO with controllable oxidation levels.

Flexible self-supported laser-induced graphene (LIG) electrode devices were facilely fabricated through laser ablation technique by employing commercial polyimide film as the precursor material. Compared with the widely used traditional glassy carbon electrodes, the resulted LIG electrodes displayed abundant porous structure and surface defects. Notably, the onestep yielded LIG electrode devices were endowed with large electrochemically active surface area and accelerated electron transfer ability. Benefiting from its superior electrochemical property, these unmodified LIG electrodes exhibited remarkable enhanced electrochemical oxidation reactivity toward the food additive molecule Allura Red. Based on the augmented oxidation signal of Allura Red molecules on the LIG electrodes, a novel electrochemical sensor with high sensitivity for the detection of Allura Red was successfully developed. The sensor demonstrated a linear detection range spanning from 5 nM to 1 μM and exhibited a detection limit as low as 2.5 nM. Besides, the sensitivity was calculated to be 240.62 μA μM−1 cm− 2. More importantly, the sensor manifested outstanding stability, reproducibility, and practicality, further emphasizing its potential for real-world application.

In order to predict the process window of laser powder bed fusion (LPBF) for printing metallic components, the calculation of volumetric energy density (VED) has been widely calculated for controlling process parameters. However, because it is assumed that the process parameters contribute equally to heat input, the VED still has limitation for predicting the process window of LPBF-processed materials. In this study, an explainable machine learning (xML) approach was adopted to predict and understand the contribution of each process parameter to defect evolution in Ti alloys in the LPBF process. Various ML models were trained, and the Shapley additive explanation method was adopted to quantify the importance of each process parameter. This study can offer effective guidelines for fine-tuning process parameters to fabricate high-quality products using LPBF.

The laser power has been continually increased since the laser was developed in the mid-20th century. Achieving higher laser power requires not only enhancing the cooling performance of laser systems but also addressing the potential degradation of optical characteristics due to thermal deformation induced by laser beam absorption in a mirror. This study delves into the thermal deformation characteristics of mirrors in high-power laser systems. To minimize thermal deformation by heat absorption, Zerodur, known for its low coefficient of thermal expansion, was employed as the mirror material. Various configurations including circular, rectangular, and spline shapes were implemented on a solid mirror structure. Furthermore, two different diameter of a mirror, 300mm and 400mm, were considered to investigate the size effect of the high-power laser beams. Also, three different transmitted beam power were adopted: 50W, 250W, and 500W. Based on the finite element analysis for the thermal deformation, the deformation characteristics of the different types of mirror structures were investigated and analyzed for high-power laser systems.

The adhesive design of a fast steering mirror transmitting a high power laser is one of the important design elements that affect optical aberration of the mirror surface. In this paper, we designed the adhesive part to avoid the high power laser beam of the FSM system. Stiffness and wavefront error are trade-off relationships and an optical design was derived to maintain the wavefront error of the mirror surface at high temperatures while satisfying the bandwidth of the FSM system. For the optimal design of the mirror bonding position, structural analysis was conducted using ANSYS and wavefront error analysis was performed using Zernike polynomial code. Through those analysis, FSM most effective at an angle 60 degrees and a distance of 46mm.

Fundamental aspects of creating passivation layers for corrosion resistance in nuclear engineering applications, specifically the ability to form complete layers versus porous ones, are being explored in this study. Utilizing a laser ablation technique, 1,064 nm fire at 10 Hz with 60 pulses per shot and 0.5 mm between impact points, aluminum samples are treated in an attempt to create a fully formed passivation layer that will be tested in a LiCl-KCl eutectic salt. By placing these samples into an electrochemical environment mimicking a pyroprocessing system, corrosion rates, resistances and material characteristics are tested for one week and then compared between treated and untreated samples. In initial testing, linear sweep voltammetry indicates corrosion current density for the untreated sample at −0.038 mA·cm−2 and treated samples at −0.024 mA·cm−2 and −0.016 mA·cm−2, respectively. This correlates to a control sample corrosion rate of −0.205 mm·yr−1 and treated rates of −0.130 mm·yr−1 and −0.086 mm·yr−1 for samples 1 and 2. In addition, electrochemical impedance spectroscopy circuits show application of a longer-lasting porous passivation layer on the treated metal, compared to the naturally forming layer. However, the current technique fails to create a uniform protection layer across the sample.

The emergence of ferrous-medium entropy alloys (FeMEAs) with excellent tensile properties represents a potential direction for designing alloys based on metastable engineering. In this study, an FeMEA is successfully fabricated using laser powder bed fusion (LPBF), a metal additive manufacturing technology. Tensile tests are conducted on the LPBF-processed FeMEA at room temperature and cryogenic temperatures (77 K). At 77 K, the LPBF-processed FeMEA exhibits high yield strength and excellent ultimate tensile strength through active deformation-induced martensitic transformation. Furthermore, due to the low stability of the face-centered cubic (FCC) phase of the LPBFprocessed FeMEA based on nano-scale solute heterogeneity, stress-induced martensitic transformation occurs, accompanied by the appearance of a yield point phenomenon during cryogenic tensile deformation. This study elucidates the origin of the yield point phenomenon and deformation behavior of the FeMEA at 77 K.

This study explores the profound impact of varying oxygen content on microstructural and mechanical properties in specimens HO and LO. The higher oxygen concentration in specimen HO is found to significantly influence alpha lath sizes, resulting in a size of 0.5-1 μm, contrasting with the 1-1.5 μm size observed in specimen LO. Pore fraction, governed by oxygen concentration, is high in specimen HO, registering a value of 0.11%, whereas specimen LO exhibits a lower pore fraction (0.02%). Varied pore types in each specimen further underscore the role of oxygen concentration in shaping microstructural morphology. Despite these microstructural variations, the average hardness remains consistent at ~370 HV. This study emphasizes the pivotal role of oxygen content in influencing microstructural features, contributing to a comprehensive understanding of the intricate interplay between elemental composition and material properties.

Nasopharyngeal stenosis is defined as a morphological transition of narrowing at the nasopharyngeal region. A 2-yearold, castrated male, Korean short hair cat was referred to the animal medical center, Gyeongsang National University. According to clinical signs, diagnostic imaging, and physical examination, nasopharyngeal stenosis was diagnosed. The staphylectomy was performed using a CO2 laser, and there were not any post-operative complications. The patient was discharged in two days. This report describes the case of nasopharyngeal stenosis in cat and represents that laser ablation could be a good option for surgical management of the nasopharyngeal region with a low complication rate.

Titanium constitutes approximately 60% of the weight of steel and exhibits strength comparable to steel's but with a higher strength-to-weight ratio. Titanium alloys possess excellent corrosion resistance due to a thin oxide layer at room temperature; however, their reactivity increases above 600°C, leading to oxidation and nitridation. Welding titanium alloys presents challenges such as porosity issues. Laser welding minimizes the heat-affected zone (HAZ) by emitting high output in a localized area for a short duration. This process forms a narrow and deep HAZ, reducing the deterioration of mechanical properties and decreasing the contact area with oxygen. In this study, fiber laser welding was conducted on 8.0mm thick Ti-6Al-4V alloy using the Bead On Plate (BOP) technique. A total of 25 welding conditions were experimented with to observe bead shapes. The results demonstrated successful penetration within the 0.792mm to 8.000mm range. It was concluded that this experimental approach can predict diverse welding conditions for Ti-6Al-4V alloys of various thicknesses.

Liquified hydrogen is considered a new energy resource to replace conventional fossil fuels due to environmental regulations by the IMO. When building tank for the storage and transportation of liquified hydrogen, materials need to withstand temperatures of -253°C, which is even lower than that of LNG (-163°C). Austenitic stainless steel mainly used to build liquified hydrogen tank. When building the tanks, both the base material and welding zone need to have excellent strength in cryogenic condition, however, manual arc welding has several issues due to prolonged exposure of the base material to high temperatures. Laser welding, which has some benefits like short period of exposure time and decrease of thermal affected zone, is used many industries. In this study, laser bead on plate welding was conducted to determine the laser butt welding conditions for STS 304 and STS 316L steels. After the BOP test, cross-section observations were conducted to measure and compare four bead parameters. These tendency result of laser BOP test can be used as conditions laser butt welding of STS 304 and STS 316L steel.

Research into lightweighting to improve vehicle fuel efficiency and reduce exhaust emissions continues as environmental regulations become increasingly stringent. Magnesium alloys, chosen for their lightweight properties, are more than 35% lighter than aluminum alloys and also exhibit excellent mechanical characteristics. While magnesium alloys are commonly utilized in arc welding processes like GTAW and GMAW, they pose challenges such as high residual stresses and welding defects. Laser welding, on the other hand, offers the advantage of precise heat input, enabling deep and high-quality welds while minimizing welding distortion. In this study, fiber laser welding was employed to weld a 4.0mm thick AZ31B-H24 using the Bead on Plate technique. A total of 10 different welding conditions were tested with fiber laser welding, and the cross-sections of the weld beads were examined. Weld bead shapes were measured based on five parameters. The results allowed for an evaluation of the weldability of AZ31B-H24 using fiber laser welding.

항만 내 선박과 부두의 사고를 예방하기 위하여 통항 및 접안 안전성 평가를 통하여 안전한 부두가 건설되어 관리하고 있으나, 선 박의 접안 및 계류 과정에서 선박이 부두에 충돌하거나 로프로 인한 인명사고의 발생 등 예측할 수 없는 사고들이 종종 발생한다. 자동계류장 치는 선박의 신속하고 안전한 계류를 위한 자동화된 시스템으로 로봇 매니퓰레이터와 흡착 패드로 구성된 탈/부착 메커니즘을 가지고 있다. 본 논문은 자동계류장치의 흡착 패드의 위치 및 속도제어에 필요한 선체와의 변위 및 속도 측정 시스템을 다룬다. 자동계류장치에 적합한 측 정 시스템을 설계하기 위하여, 본 논문은 우선 센서의 성능 및 실외 환경적 특성 분석을 수행한다. 다음으로 이러한 분석 결과를 토대로 실외 부두환경에서 설치되는 자동계류장치에 적합한 변위 및 속도 측정시스템의 구성 및 설계 방법에 대해 기술한다. 또한 센서의 측정상태 감지 및 속도 추정을 위한 알고리즘을 제시한다. 제안된 방법은 다양한 속도 구간에서의 변위 및 속도 측정 실험을 통해 그 유용성을 검증한다.