In this study, we investigated the change in fracture properties after friction stir welding on Al606. In the L-T direction test, the fracture toughness of the unwelded base material was 275 MPa, and the specimen subjected to friction stir welding (FSW) was 227 MPa, showing that the fracture toughness decreased significantly with friction stir welding. In the T-L direction test, the difference between the base material and the weld material was not large, but the fracture toughness was shown to decrease during welding. In the comparison of the L-T direction and the T-L direction, it was found that both the base material and the weld material showed high fracture toughness in the L-T direction.In this study, the following conclusions were obtained after friction stir welding of Al 6061-T6.

When cooking, especially during processes such as grilling or frying, harmful gases are generated. Among them, fine dust is a major factor causing lung cancer, and to eliminate it, range hoods are commonly used. Particularly, when using portable cooking device like gas stoves, it is even more challenging to remove fine dust. In this study, a cooking device was developed to combine steam and cooled air in the air-curtain area to recover fine dust generated during the cooking process, allowing it to be collected as food. The device was evaluated according to criteria defined independently and validated through experiments. As a result, all criteria were satisfied within the specified range.

Safe operation of freight vehicles is an important issue for drivers, cargo, and other road users. In particular, the center of gravity of a freight vehicle is directly related to the stability of the vehicle, and this can fluctuate in real time depending on weight changes. Every time a freight vehicle loads or unloads cargo, its center of gravity changes, and these changes greatly affect the risk of vehicle rollover. We researched a continuous center of gravity measurement system for freight vehicles for safe driving.

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.

For motor controller designers, building a simulation environment is not a difficult process. After verifying the controller by simulation, it is common to select 20kHz for the current control loop, 1kHz for the speed loop, and 100Hz for the position loop when implementing the actual HW embedded system. This is because maximized cycles (20kHz) for each control loop are unnecessary in control theory and are a waste of cost and HW resources. However, in a simulation environment, each loop will often have the same control cycle (20kHz maximum). This is because we think it is unnecessary to reflect this part in the simulation. In this paper, it is shown that the difference in the sampling time of each control loop makes a big difference in the simulation result, and as a solution, it is proposed to apply LPF to the position loop output stage. In the process, the reasons for the differences were analyzed, and the effect of LPF, the reason for application, and the feasibility of implementation were proved by actual software coding.

In alignment with South Korea's “3020 Renewable Energy Expansion Plan,” this study focuses on the developing large-scale floating wind turbines. It addresses the challenges of increased size and cost in floating structures for wind turbines over 10MW. This paper details the preliminary design of a novel floating substructure utilizing composite materials(ie, EVA). Structural analysis was performed using ABAQUS, accounting for both typical and extreme wind conditions. Results from the analysis validate that the substructure design is adequately feasible for implementation.

This study investigates the utilization of existing CCTV networks for road traffic volume measurement, a key indicator of road infrastructure utility. Traditionally, traffic studies, which are costly and time-consuming, are divided into continuous or ad-hoc surveys. By leveraging current CCTV systems, the proposed method eliminates the need for new installations, conserving resources and increasing efficiency. Preliminary results indicate that this approach offers a time and cost-effective alternative for traffic assessments, with the potential to transform traditional survey techniques.

Power converter devices require a high level of quality because they have a high direct connection with vehicle operation. Therefore, structural bonding was carried out by friction stir welding with excellent mechanical properties. Friction stir welding can cause structural deflection depending on the load of the welding tool, so it is important to control this for high quality flatness. In this study, pre-welding was performed before welding to minimize deflection generated during welding. And deflection reduction data according to the location of pre-welding were analyzed through dynamic analysis. As a result, based on computerized data rather than experimental data an optimized position of pre-welding was secured to minimize the deflection that occurs during friction stir welding. Through this, a process guide that enables high quality structural bonding was presented.

This study investigates the enhancement of surface precision and dimensional accuracy in STS 316L oval pipes through the application of magnetic abrasive finishing. The experiment involves the modification magnetic pole shapes(A, B, C, D) and a comprehensive analysis of their impact on surface quality. Key parameters include magnetic abrasive KX#320, iron powder, aluminum oxide, light oil, a test specimen rotating at 600rpm, and periodic injection of polishing liquid, a permanent magnet Nd-Fe-B, and magnetic pole steel 1018, reciprocating distance 20mm, and a feed rate 1mm/sec over a 32minutes duration with measurements every 4minutes. The results demonstrate significant variations in surface quality based on magnetic pole shape, with specific configurations demonstrating superior precision and smoothness from the initial surface 0.32μm to 0.06μm.

본 연구는 탈진실 시대에 한국의 공영방송이 추구해야 할 디지털 미디 어 리터러시의 개념과 능력은 무엇이며 시민의 미디어 리터러시 역량 증 진을 위해 우선순위에 두어야 할 핵심 가치가 무엇인지 고찰했다. 이를 위해 대표적인 공영방송의 준거점으로 손꼽히는 영국 BBC와 국내 교육 공영방송 EBS가 제공하는 미디어 리터러시에 관한 콘텐츠를 비교했다. 연구 결과, BBC와 EBS는 공통으로 비판적 이해(critical thinking)를 미 디어 리터러시의 핵심 가치로 보았다. 특히, BBC는 신뢰할 수 있는 뉴스 와 오정보나 허위 정보를 판단할 수 있는 능력, 소셜미디어의 알고리즘 과 에코 체임버(echo chamber)가 사람들의 편향성에 미치는 영향을 이 해하는 능력과 비대면 커뮤니케이션에서 혐오나 증오 표현 등의 부적절 한 언어적 비언어적 행동이 타인에게 미치는 영향에 대해 인지하는 능력 을 미디어 리터러시의 핵심 역량으로 보았다. 결론적으로, ‘탈진실’ 시대 에 학자, 교육자, 전문가가 협력해 국내 교육 현실과 미디어 환경에 맞는 미디어 리터러시 개념을 정립하고, 이에 따라 청소년과 시민의 미디어 리터러시 역량 증진과 디지털 웰니스(Wellness)를 위한 공영방송의 콘텐 츠 개발이 필요할 것으로 보인다.

With the mandatory implementation of ESC for trucks starting in 2023, domestic truck manufacturers in South Korea are advocating for a relaxation of the maximum safe slope angle to achieve cost savings. However, there is a lack of research on the dynamic safety of trucks based on ESC installation and the relaxation of the maximum safe slope angle. This study evaluates the relationship between static safety factor (SSF) and the maximum safe slope angle, analyzing the dynamic stability of trucks through simulation considering various experimental variables. The results quantitatively demonstrate the impact of relaxing the maximum safe slope angle on dynamic safety and provide recommendations for future safety regulations.

The heat transfer characteristics of double-pipe spiral heat exchanger were investigated by various curvature sizes, experimentally. The three different sizes of heat exchanger were made and tested with water as a working fluid to analyze the heat transfer characteristics. The heat transfer rates, overall heat transfer coefficient and pressure drop were analyzed with various heat exchanger sizes (i.e., curvature ratios). As result, the heat transfer rate increased with increasing the size of the heat exchanger as the flow rate increased due to increasing the area size of heat transfer. However, the overall heat transfer coefficient and pressure drop increased with decreasing the heat exchanger size (i.e., increased curvature ratio) due to the enhanced centrifugal force and inertia.

Internal combustion engine is the main source of environmental pollutants and therefore advanced technology is required to reduce harmful elements from the exhaust gases all over the world. Especially, when the exhaust gas is released from the automotive muffler, exhaust noise has many bad influence on the surrounding environment. In order to reduce the exhaust noise, it is necessary that automotive muffler must be designed for best exhaust efficiency. The sound insulation room was installed for the analysis of an acoustics characteristics of the noise from automotive muffler, in this study. Exhaust gas noise, noise distribution characteristics, pressure and temperature of exhaust gas were investigated with the change of annulus temperature of air cooled annulus automotive muffler and cooled annulus automotive muffler. The following results were obtained with this study. From the frequency analysis of automotive muffler, high noise distribution was observed in the range 100~2000Hz. It means that the noise in this range has an dominate influence for the overall noise. Noise reduction of automotive muffler was affected by the temperature of annulus. It is caused the result that the high temperature and pressure of exhaust gas are changed lower by the drop of annulus temperature. The tendencies of noise, the temperature and pressure of exhaust gas are similar to the performance curve of engine. Exhaust gas pressure is determined by the r.p.m. of engine and affected by the cooling performance of automotive muffler.

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.

In this study, we examined the effect of orifice diameter on atomization performance such as SMD(Sauter Mean Diameter), MMD(Mass median diameter), particle size distribution, spray distance, and spray angle when water was sprayed through a siphon nozzle. In addition, the behavior characteristics of spray were analyzed using the CFD(Computational Fluid Dynamics) commercial program. In the downstream direction of the flow, the dispersion and diffusion power of the droplets increased, greatly improving atomization performance. The spray spread in the radial direction when the jet velocity of water increased. As a result, atomization performance improved as the jet velocity increased.

This study chiefly aims to clarify important items to establish design guidelines for the habitability of temporary housing. Though prevention of occurring disasters would be the best way, readiness for the protection of suffering psychological damage is essential to construct emergency shelters and temporary housing. Temporary housings until now have raised second psychological injury, due to the lack of community spaces between victims by the disasters. It is meaningful to make fundamental data for establishing design guidelines for the habitability of temporary housing through the advanced countries for the disaster protection.

전쟁 시 각국은 고대로부터 마비전을 추구하여 적의 중심을 지향하여 최소의 희생으로 승리하고자 하였다. 또한 특수작전부대는 합동작전의 핵심부대로 각국은 특수작전부대를 증가하고 있는 추세이다. 따라서 본 연구의 목적은 전쟁양상의 변화와 더불어 마비전이 진화함에 따라 전쟁 시 마비전 사례분석을 통해 특수작전부대의 역할을 도출하고, 미래 다영역 작전 시 마비전 수행을 위한 특수작전부대의 운용방향을 제시하는 데 있 다. 연구 방법은 문헌연구를 통한 질적연구와 사례를 분석 후 비교하였다. 연구범위는 제2차 세계대전으로부터 걸프전, 이라크전을 분석하였고 미래 운용방향은 미국의 다영역작전 시 특수작전부대 운용을 연구하여 한국군에 적용하였다. 연구 결과, 마비전은 초기의 물리적 마비로부터 물리적 마비 +체계무력화+심리적 마비로 진화하며 발전하였고, 특수작전부대는 마비 전 수행에 결정적으로 기여하였으며 그 중요성은 더욱 증가하고 있음을 확인할 수 있었다. 따라서 한국군 특수작전부대는 미래 다영역작전에서 도 마비전을 수행하기 위해 지속적인 마비전 수행개념과 이를 위한 조직 편성 및 무기체계의 발전이 요구되고 있다.

This study investigated the noise reduction effect according to the structure of the sound-absorption and insulating materials in order to maximize the noise reduction effect in various noise environments. For this purpose, the transmission loss according to the change in hole size of the performated plate in sound-absorption and insulating board was predicted using an CAE model. The sound-absorption and insulating board was modeled and the computation of the transmission loss was performed after applying the physical properties and boundary conditions. The pure sounds of 32Hz to 4,000Hz were generated, and the analysis was performed by changing the diameter and pitch of the perforated plate. It was confirmed that the influence of the diameter and pitch of the perforated plate is closely related to the structure that make up the sound-absorption and insulating material. In order to effectively reduce the variously changing noises, it is believed that a method of improving transmission loss for each frequency band of interest is needed by changing the structure of the sound-absorption and insulating material so that the diameter and pitch of the perforated plate can be changed.

In this study, a high-resolution integrated real-time visualization device using surface plasmon resonance was designed and considered to overcome the measurement limitations of existing optical systems. For precise measurements, resonance angle and reflectivity were calculated using theoretical equations, and the designed surface plasmon resonance visualization system was verified by comparison with experimental values using a He-Ne laser. Surface information of the droplet was acquired using polarized, single-wavelength converted white light, and quantified through image processing. As a result of the experiment, it was confirmed that when light with a wavelength of 632.8 nm is incident on the Kretchmann structure prism-metal thin film-dielectric (air/water), it is not totally reflected at an angle above the critical angle and the reflectivity is rapidly reduced due to the surface plasmon resonance phenomenon. As a result of quantifying the image, it was confirmed that the droplet reflectivity was similar to the theoretical reflectivity at each resonance angle.

For the Floating Photovoltaic development project, economic analysis is conducted by predicting the amount of power generation in consideration of climate factors. Among the climate factors, the outside temperature increases the temperature of the module. As a result, the efficiency of the module is reduced. Due to global warming, the outside temperature is rising every year, when estimating the amount of power generation over the next 20 years, a more accurate prediction will be possible only when considering the temperature rise.