The purpose of this study is to establish a foundation for design guidelines by characterizing the behavior of a CRCP tapered-end terminal connected to a mainline CRCP. A pilot construction was conducted to determine the deformation and displacement within the CRCP transverse crack, at the end and at the connection. Various measuring instruments were installed and monitored to evaluate these trends. Although the reinforcement stress was lower than that of the main line, the shrinkage and expansion at the ends showed no significant deviation from the main line CRCP. Tie-bar measurements indicated that tensile deformation occurred on the inner side near the longitudinal construction joint, whereas compressive deformation occurred on the outer side. Furthermore, these results indicated the superposition of bending induced by longitudinal displacement and tension caused by transverse displacement along the LCJ. Additionally, the strain increased as the tie-bar installation propagated closer to the CRCP end. Through regression analysis, the thermal displacement at the end expansion joint was determined to be 0.1122 mm per unit temperature. The longitudinal displacement along the longitudinal construction joint was selected at the ends and attenuated rapidly within a range of 2–4 m. The recorded daily and seasonal displacements at the end were 0.38 and 2.73 mm. Although the longitudinal reinforcement strain at the tapered ramp terminal was lower than that at the main line, the end displacement exhibited a similar trend. To address the excessive bending observed near CRCP expansion joints, this study proposed a method for determining tie-bar offset distances, thereby establishing a technical basis for improved pavement design at tapered sections.

This paper presents an experimental investigation into multi-diode open-circuit faults in the rotating rectifiers of brushless synchronous generators. Unlike single-diode faults, multi-diode faults introduce complex electrical behavior by reconfiguring conduction paths and altering rectifier topology. Representative fault scenarios, categorized from Class 3 to Class 8 are examined under no-load conditions to isolate excitation system dynamics. Key electrical quantities, including exciter armature currents (  -  ), rectifier output voltage ( ), main field current ( ), exciter field current ( ), and generator terminal voltage (  ), are evaluated. The results show that electrical characteristics are governed by the effective conduction paths and the resulting rectifier structure rather than the number of faulty diodes. Depending on the fault condition, the rectifier transitions move transitions from asymmetric three-phase rectification to single-phase full-wave or half-wave rectification. These structural transitions lead to amplitude reduction and the emergence of dominant frequency components, particularly at 60 Hz and 120 Hz. The findings provide a structural interpretation and electrical characteristic analysis of multi-diode faults.

Brushless excitation systems are widely used in marine synchronous generators due to their high reliability and reduced maintenance requirements. In these systems, the rotating rectifier converts the three-phase AC output of the exciter into DC current for the main field winding. However, faults in the rotating rectifier, particularly a single diode open-circuit fault, can degrade excitation performance without immediately triggering protective devices, making early detection difficult. This paper experimentally investigates the effects of a single rotating rectifier diode open-circuit fault on the excitation system and voltage formation of a brushless synchronous generator under no-load operating conditions. The no-load condition minimizes the influence of armature reaction and load current, allowing fault-induced excitation behavior to be clearly isolated. A brushless excitation system was implemented using three synchronous machines of identical rating, and a single diode open-circuit fault was intentionally introduced in the rotating rectifier. Excitation-related electrical quantities related to the excitation system, including DC excitation current and voltage, exciter armature currents, and generator terminal voltage, were measured and compared before and after the fault. Experimental results demonstrate that the single diode open-circuit fault causes reduction in the average excitation current and introduces low-frequency ripple components in the excitation current waveform while the terminal voltage reduction remains limited under no-load conditions. These results indicate that excitation-related electrical signals can serve as effective indicators for the detection of rotating rectifier diode faults in brushless synchronous generators.

Carbon fibers (CFs) are notable for their lightweight, high strength, and excellent electrical conductivity, making them promising for applications like electrical wiring. However, integrating CFs into copper-based wiring systems faces challenges, particularly regarding conductivity loss in fractured CFs. This article discusses a two-step experiment to enhance electrical and mechanical connection. Electrothermal-induced solvent evaporation (EISE) and meniscus-confined electrochemical deposition (MECD) were identified as effective methods for welding fractured CFs and were successfully implemented in open-air environment. Deposition of carbon nanotubes (CNTs) around the fiber improved conductivity by reducing fiber-tofiber contact resistance and creating a metal-like surface. Microstructural analysis and EDS analysis revealed that the CNT cladding exhibited high density and fewer irregularities and bulges in the joint area. Furthermore, the CNTs were tangled, forming a less organized structure compared to the original CF. In contrast, the Cu cladding exhibited paint-like coverage, significant irregularities, bulges, and cracks but maintained a small thickness. Electrical testing revealed that the average resistance of a single joined fiber decreased to resistance of 11.45 Ω and an electrical resistivity of 2.27 Ω/m, demonstrating improved electrical conductivity. Under optimal conditions, the joined fibers exhibited plastic fracture, and all joints showed improved performance except joint 1.e-g enhanced mechanical strength and stress tolerance.

메탄화 공정은 탄소 포집 및 활용(CCU) 기술의 하나로, 탄소중립 달성을 위한 핵심 기술이다. 본 연구는 메탄화 반응기 배출가스에서 생성가스인 메탄과 미반응 수소를 분리하기 위한 가스 분리 시스템 설계를 위한 사전 연구로, 소형 막 모듈을 이용한 2단 분리막 시스템을 설계⋅제작하고 시험 가스인 질소-수소 혼합가스에 대한 분리 성능을 실험적으로 평가하 였다. 1단 막 모듈에서는 질소-수소 혼합가스에 대한 혼합 가스 선택도를 측정하였으며, 1단 및 2단 막 모듈 모두에서 잔류 측과 투과 측의 목표 가스 회수율 및 순도를 분석하였다. 본 연구에서 수행한 국내 A사 막 모듈의 성능 분석 결과는 향후 메 탄화 반응 가스 분리 시스템 설계 및 최적화 연구의 기초자료로 활용될 수 있다.

This study investigates the impact of solar paper panel tilt angles on the flight endurance of solar powered the drone. To address the limited flight time of conventional battery powered drones, photovoltaic solar paper panels were mounted at varying angles 0°, 15°, 30°, and 45° tested under consistent conditions. Experimental results showed that a 30° tilt angle produced the highest power output, leading to about 14% increase in flight duration compared to a flat configuration. These findings demonstrate that optimizing panel orientation significantly improves energy efficiency and drone performance. This work provides practical insight into the design of lightweight solar UAVs and highlights the feasibility of simple tilt adjustments as a low complexity alternative to active solar tracking systems.

본 연구는 선박 기관 냉각수 계통의 부식 관리를 해양사고 예방 관점에서 분석하였다. 해양사고 재결서 분석을 통해 관련 주요 사고 원인을 도출하고, 부식 억제제 농도 변화가 부식 거동에 미치는 영향을 실험적으로 평가하였다. 중앙해양안전심판원 재결서 950건을 텍스트 마이닝과 대규모 언어모델로 분석한 결과, 기관손상 사고 중 냉각수 계통 관련 사례의 비중이 가장 높았으며 주된 원인은 관리 소 홀과 점검 미흡 등 인적 요인으로 확인되었다. 이 분석을 토대로 선박 냉각수 관리의 핵심 요소인 부식 억제제의 첨가와 농도 유지가 부 식 거동에 미치는 영향을 구상흑연주철(FCD-500)을 대상으로 평가하였다. 아질산염 기반 억제제 농도를 0에서 19,000 ppm 범위로 설정하 고, 침적시험과 전기화학 기법을 적용하여 부식 특성을 비교하였다. 권장 농도 13,000 ppm에서는 균일부식과 국부부식이 모두 효과적으로 억제되었고 3000에서 7000 ppm의 저농도 구간에서는 국부부식으로 인한 설비 손상 위험이 증가하였다.

The use of aluminum-based hybrid metal matrix composite (HMMC) materials, especially in engine components like pistons, is intended to improve wear resistance and overall performance. Crucial tribological indicators, such as wear and friction coefficients, underscore the significance of these materials. However, present aluminum alloys have limited wear because of clustered reinforced particles and relatively high coefficients of thermal expansion (CTE), resulting in inadequate anti-seizure properties during dry sliding conditions. This research introduces a novel “Hybrid Metal Matrix Composite of Al7068 Reinforced with Fly Ash-SiC-Al2O3”. Al7068 is employed for its superior strength-to-weight ratio and specific modulus, which is ideal for components exposed to cyclic loads and varying temperatures. The integration of fly Ash (FA), silicon carbide (SiC), and alumina (Al2O3) as reinforcements enhances wear resistance, diminishes particle clustering, improves stiffness, mitigates CTE discrepancies, and fortifies the composite against strain and corrosion, thereby enhancing its overall performance. The Stir-casting method was used with optimized reinforcement percentages (10 % total), and comprehensive evaluations through wear tests and mechanical property analyses determined the composite's optimal composition. The proposed HMMC variant with the most suitable reinforcement percentage exhibited enhanced engine piston functionality, reduced wear, low deformation of 0.20 mm, and a comparatively higher ultimate tensile strength of 190 megapascals (Mpa).

Fault detection in electromechanical systems plays a significant role in product quality and manufacturing efficiency during the transition to smart manufacturing. Because collecting a sufficient number of datasets under faulty conditions of the system is challenging in practical industrial sites, unsupervised fault detection methods are mainly used. Although fault datasets accumulate during machine operation, it is not straightforward to utilize the information it contains for fault detection after the deep learning model has been trained in an unsupervised manner. However, the information in fault datasets is expected to significantly contribute to fault detection. In this regard, this study aims to validate the effectiveness of the transition from unsupervised to supervised learning as fault datasets gradually accumulate through continuous machine operation. We also focus on experimentally analyzing how changes in the learning paradigm of the deep learning model and the output representation affect fault detection performance. The results demonstrate that, with a small number of fault datasets, a supervised model with continuous outputs as a regression problem showed better fault detection performance than the original model with one-hot encoded outputs (as a classification problem).

The purpose of this study is to measure and analyze the number of chest compressions, chest compressions, depth of chest compressions, ventilation, duration of interruption, and accuracy in college students when eyewitness cardiac arrest occurs. The results of the experiment are as follows.(1) The result of the difference in the number of chest compressions was that A was a 20-year-old woman with an average of 114 chest compressions. E was a 22-year-old man with 96 chest compressions, and J was a 24-year-old woman with 109 chest compressions. (2) The result of the difference in chest compressibility depth was that A was a woman in her 20s with an average chest compression depth of 5.0 to 5.2 cm, E was a man in his 20s with an average chest compression depth of 5.0 to 5.4 cm, and J was a woman in her 20s with an average chest compression depth of 5.1 to 5.5 cm. (3) Ventilation was performed for A, E, and J. (4) CPR discontinuation time (second) was performed for a 20-year-old woman for 0 seconds, E was for a 22-year-old man for 5 seconds, and J was a 24-year-old woman for 5 seconds or less. (5) CPR accuracy was found to be 95.2% for a 20-year-old woman, E was found to be a 22-year-old man for 79.6% for a 22-year-old man, and J was found to be 86% for a 24-year-old woman on average. In order to properly cope with an emergency situation in which cardiac arrest occurs, it is confirmed that CPR practice should be sufficiently performed in advance to improve the accuracy of cardiac pressure, and CPR should be performed when cardiac arrest patients occur by maintaining skills through steady retraining.

국내 도심지에 적용하고 있는 중앙버스정류장의 포장은 주로 아스팔트 포장으로 시공되어 있으나 중차량인 버스의 하 중으로 인해 포장 파손 사례가 증가하여 시민들의 안전에 악영향을 미치고 있으며 유지보수 비용이 매년 증가하고 있다. 서울시에서는 이러한 문제를 해결하기 위해 국내 최초로 중앙버스정류장 신설 구간에 현장타설 방식으로 연속철근 콘크 리트 포장(CRCP)을 시공하였다. 본 연구에서는 이러한 구간의 연속철근 콘크리트 포장에 대한 이동차량 하중에 의한 동 적 거동 특성을 분석하고자 포장 슬래브에 콘크리트 변형률계를 설치하고 덤프트럭을 통과시키며 동적 하중 재하 실험 을 수행하였다. 실험에서는 이동차량의 속도를 다양하게 변화시켜 차량 속도에 따른 포장 슬래브의 동적 거동을 비교 분 석하였으며 이동차량이 CRCP의 여러 위치에서 정지하도록 하여 정지 위치에 따른 거동도 분석하였다. 실험 결과, 차량 이 CRCP를 통행할 경우 차량 속도 및 정지 위치에 따른 포장 슬래브의 동적 변형률은 매우 유사한 것으로 분석되었다.

내부 폭발 조건에서 화약이 폭발하게 되면, 연소되지 못한 화약이 공기와 반응하여 추가적인 에너지를 발생시키는 현상을 재연소 현상이라고 한다. 재연소 현상은 최대 폭압과 충격량을 높이는 역할을 하기 때문에 전산수치해석을 이용한 폭압 전파 특성을 예측을 수행할 때 반드시 고려해야 한다. 본 논문에서는 재연소 조건을 고려한 내부폭발 전산수치해석 방법을 검증하기 위해 3종류의 서로 다른 형태의 내부폭발 실험과 비교하였다. 그 결과, 재연소 조건을 적용하지 않았을 때는 최대 폭압과 충격량 차이가 최대 45.13%, 68.54% 발생하였으나, 재연소 조건을 고려하여 해석을 수행하였을 경우 최대 폭압과 충격량의 차이가 각각 18.08%, 15.17%로 크게 줄어들었다.

This study investigates the thermal expansion characteristics of hydroxyl-terminated polybutadiene(HTPB) based solid propellants, focusing on batch-to-batch variability and accelerated aging effects. Coefficient of thermal expansion(CTE) measurements were conducted using thermomechanical analyzer(TMA) on samples from different manufacturing batches and specimens aged at various temperatures for different durations. Results indicate variations in CTE values between batches, highlighting the significance of manufacturing process control. Accelerated aging experiments reveal minimal systematic changes in CTE, suggesting stability of thermal expansion properties under short-term thermal stress. The overall distribution of CTE values shows concentration within a specific range, indicating consistency in thermal expansion characteristics. These findings provide insights into the thermal behavior of HTPB-based solid propellants, contributing to improved missile design and lifecycle prediction models.

콘크리트 도로포장의 손상은 차량의 이동에 의한 진동, 겨울철 제설제 사용, 동결융해 작용 등이 주요 손상원인으로 나타나고 있다. 이러한 손상을 해결하기 위하여 열화 원인에 능동적으로 대응하는 보수재료 및 방법이 적용되어야 하나, 일반적으로 단면복구, 부분보 수를 반복적으로 사용함으로써, 지속적인 열화 현상의 발생으로 도로포장의 기능을 상실하게 된다. 또한, 기존에 사용되고 있는 보수 재료 중 무기계 보수재료는 폴리머 모르타르, 에폭시수지 모르타르 등이 있다. 이러한 재료는 높은 압축강도를 가지고 있으나, 취성 및 부착력이 약한 단점을 나타내고 있다. 따라서 본 연구에서는 보통포틀랜드시멘트(Ordinary Portland Cement), 칼슘알루미네이트계 재 료인 칼슘설포알루미네이트(Calcium Sulfo Aluminate) 및 비정질 알루미네이트(Amorphous Calcium Aluminate)를 사용한 보수 모르타르의 압축강도 및 내동해성을 평가하였다. 보수 모르타르의 압축강도를 분석한 결과, 비정질 알루미네이트를 사용한 보수모르타르의 압축강 도가 보통포틀랜드시멘트 및 칼슘설포알루미네이트를 사용한 보수 모르타르보다 우수하게 나타나는 것을 확인하였다. 한편, 보수 모르 타르의 내동해성 평가는 ASTM C 666 A법에 준하여 실험을 진행하였다. 그 결과, 칼슘설포알루미네이트 및 비정질 알루미네이트를 적용한 보수 모르타르의 상대동탄성계수가 300사이클에서 약 90%이상으로 나타나 보통포틀랜드시멘트를 사용한 보수 모르타르보다 우수한 내동해성을 나타내었다. 따라서, 칼슘설포알루미네이트 및 비정질 알루미네이트를 적용한 보수 모르타르는 우수한 압축강도 및 내동해성을 나타냄으로써 도로포장의 보수재료로 사용이 가능할 것으로 판단된다.

본 연구에서는 연속철근 콘크리트 포장(CRCP) 본선차로에 줄눈 콘크리트 포장(JCP) 길어깨가 적용되었을 경우에 타이바와 슬래브에 작용하는 응력을 완화시키고자 창녕밀양 고속도로 건설사업단 1공구에 타이바 규격 및 배치에 따른 3가지 경우를 구성하여 시험시공 을 실시하였다. 각 경우마다 타이바에 철근 변형률계를 설치하고 길어깨 포장에 콘크리트 변형률계를 설치하여 거동 분석을 수행하였 다. 분석 결과, 모든 경우에서 타이바와 콘크리트 슬래브의 응력이 강도에 비해 작게 분석되어 공용성에는 문제가 없음을 확인하였다. 향후 주기적인 거동 분석을 통해 최적의 타이바 배치 및 규격을 설계하여 콘크리트 포장의 공용성을 향상시키고자 한다.