PURPOSES : In this study, a method to use magnesium phosphate ceramic (MPC) concrete for the surface maintenance of airport pavements with jointed concrete is developed. METHODS : To investigate the application of a material incorporated with MPC for the surface maintenance of airport pavements with jointed concrete, structures with various cross-sections and thicknesses were constructed. The cross-section of the structure was modeled for the surface maintenance of four types of pavements and typical pavement construction processes, such as cutting, cleaning, production and casting, finishing, hardening, and joint reinstallation. Subsequently, the hours required for each process was determined. RESULTS : The MPC concrete used for the surface maintenance of airport pavements with jointed concrete demonstrate excellent performance. The MPC concrete indicates a compressive strength exceeding 25 MPa for 2 h, and its hydration heat is 52.9 ℃~61.2 ℃. Meanwhile, the crushing and cleaning performed during the production and casting of the MPC require a significant amount of time. Specifically, for a partial repair process, a total of 6 h is sufficient under traffic control, although this duration is inadequate for a complete repair process. CONCLUSIONS : MPC concrete is advantageous for the surface maintenance of airport pavements with jointed concrete. In fact, MPC concrete can be sufficiently constructed using existing concrete maintenance equipment, and partial repair works spanning a cross-sectional area of 11 m2 can be completed in 1 d. In addition, if the crushing and cleaning are performed separately from production and construction, then repair work using MPC concrete can be performed at a larger scale.

This research is to study the solution to the defects in maintenance and inspection that can be predicted/prevented in advance among human factors that account for more than 70% of the causes of aviation accidents. Traditionally, mechanics have performed visual inspections of aircraft exteriors. Due to this, there were factors that affect the human ability of mechanics in aircraft maintenance and inspection, safety problems when performing the upper part of the aircraft inspection, and the difficulty of precise inspection. To improve these problems, we conduct a study on an AI drone inspection system that has deep-learned samples on aircraft damage/defects. In this paper, we describe the aircraft maintenance inspection checklist, non-destructive inspection types, types of aircraft damage and defects, deep-learning highly reliable AI drone inspection systems, and the expected effects of this technology and future applications. Through this system research, it is expected that mechanics will efficiently inspect the aircraft through the optimization of aircraft maintenance system technology to prevent aviation accidents in advance and reduce time and economic costs.

This study investigated the maintenance and management of government office building in Dongnaebu, Gyeongsangdo in the mid-19th century. In the late Joseon Dynasty, Dongraebu was an important point of national defense and a place of trade and diplomacy with Japan, so it had many government facilities. There are very few government facilities remaining today, and no structure remains. Therefore, it is possible to grasp information about the government facilities through the old materials. Currently, there are public documents related to the local government offices such as Eupji, Eupsarye, and Junggi. Through comparison between public documents, we will examine the maintenance and management of Dongnaebu government facilities in the mid-19th century. As a result of the research, Dongnaebu government facilities were supervised by department and managed like articles. In addition, the name, size, and changes were all recorded in the management of the goods, and the authority of responsibility was clearly stated. This result is because the remaining material has the purpose of preparation as an accounting book. As a result, it was found that the government facilities in the late Joseon Dynasty were managed by a systematic department with clear authority.

Predicting remaining useful life (RUL) becomes significant to implement prognostics and health management of industrial systems. The relevant studies have contributed to creating RUL prediction models and validating their acceptable performance; however, they are confined to drive reasonable preventive maintenance strategies derived from and connected with such predictive models. This paper proposes a data-driven preventive maintenance method that predicts RUL of industrial systems and determines the optimal replacement time intervals to lead to cost minimization in preventive maintenance. The proposed method comprises: (1) generating RUL prediction models through learning historical process data by using machine learning techniques including random forest and extreme gradient boosting, and (2) applying the system failure time derived from the RUL prediction models to the Weibull distribution-based minimum-repair block replacement model for finding the cost-optimal block replacement time. The paper includes a case study to demonstrate the feasibility of the proposed method using an open dataset, wherein sensor data are generated and recorded from turbofan engine systems.

연구대상판결은 크게 두 부분으로 구성되어 있다. 첫째, 민법 제663조 제2항과 제3항에 의해 도급인의 ‘하자보수청구권’과 ‘하자 보수에 갈음하는 손해배상채권’은 특별한 사정이 없는 한 수급인의 도급인에 대한 ‘공사대금채권’과 동시이행의 관계에 있고, 이로 인해 도급인이 하자보수나 이에 갈음하는 손해배상청구권을 보유하고 이를 행사하는 한 도급인의 공사비 지급채무는 이행지체에 빠지지 않는다. 둘째, 수급인의 공사비채권의 변제기는 건물의 준공, 인도일이고, 도급인의 하자 보수에 갈음하는 손해배상채권의 변제기는 도급인이 그 권리를 행사한 때인데, 도급인이 하자보수에 갈음하는 손해배상채권을 자동채권으로 하고, 수급인의 공사비잔대금채권을 수동채권으로 하여 상계의 의사표시를 한 경우, 상계적상일 다음날이 아니라 “상계의 의사표시를 한 다음날”부터 이행지체에 빠진다. 연구대상판결은 동시이행의 범위에서 전부거절설에 기초하고 있다. 그러나 전부 거절설을 취한 이유에 대해서는 밝히지 않고 있다. 그러나 연구대상판결에서 동시이행의 항변권에 기해 전부거절설을 취한 것은 i) 하자보수에 갈음한 손해배상채권과 보수채권 사이의 동시이행의 항변권은 비쌍무계약상 동시이행의 항변권에 해당하므로, ii) 제667조 제3항에서 제536조 를 준용한 취지를 살펴 그 동시이행의 항변권에 기한 이행거절의 범위를 결정할 필요가 있는데, iii) 그 준용의 취지가 하자보수에 갈음하는 손해배상채권에 기한 상계권을 대금감액적으로 행사할 수 있도록 특별히 동시이행관계를 설정한 것 이라고 보는 것이 가장 적절한 설명이 될 수 있을 것으로 보인다. 또한 상계적상일 다음날이 아니라 상계의 의사표시 다음날부터 잔여보수채무의 이행지체책임을 지도록 한 것은 i) 하자보수에 갈음한 손해배상청구에서 하자 보수비용의 확정이 현실적으로 용이하지 않다는 현실적인 문제를 고려하여 그 하자보수비용 확정 전에 보수채무의 변제기가 도래하는 상황에서 도급인이 하자보수에 갈음하는 손해배상채권에 기한 상계권을 대금감액을 위해 행사할 수 있도록 제667조 제3항에서 제536조를 준용하여 하자보수에 갈음하는 손해 배상채권에 기한 동시이행의 항변권의 행사로 보수채무 전부를 거절할 수 있다는 현실적 관점과 ii) 상계의 소급효가 전부거절설에 의한 이행지체책임의 면제이익을 뒤집을 수 없다는 이론적 관점에서 정당화될 수 있다고 본다.

Asphalt concrete(Ascon) is used to repair potholes and cracks. Special truck-mounted cargo boxes transport 200℃ asphalt concrete to repair potholes and cracks. However, long working and transportation hours to repair wide roads decrease the temperature of the asphalt concrete inside the cargo boxes. If the asphalt concrete temperature drops below 170℃, the adhesion with roads that need repair decreases. Therefore, the temperature of the asphalt concrete needs to be maintained for a long time. Conventional asphalt concrete cargo boxes are mostly burner-type models using hot air to prevent the temperature of the asphalt concrete from dropping. However, there are significant temperature differences between the asphalt concrete near and far away from the hot air, so the temperature decreases over time and leads to the disposal of large amounts of asphalt concrete. This causes waste of resources and environmental pollution. Therefore, this study proposed a heat dissipation cut-off type cargo box model to solve this problem and demonstrated its performance over conventional burner-type models through tests and analysis.

This study was described with a focus on the maintenance and management of Local Confucian School(Hyanggyo) architecture, centering around cases investigated through official documents written in the 1910s. In 1910, by the Japanese imperial rule, the regulations on Local Confucian School(Hyanggyo) property were enacted, and the income was paid solely to elementary school education expenses and ancestral rites. Through this process, many Local Confucian School(Hyanggyo) buildings were destroyed while only the space for ritual sacrifices remained by the Japanese colonial rule. In particular, as the land, which was the basis of Local Confucian School's property, was sold for various reasons, the finances gradually deteriorated. In addition, as the architectural acts that Local Confucian School preserves itself are restricted, it loses its original character. This study was of great significance that identified the intention to dispose of Local Confucian School(Hyanggyo) property by Japanese imperialism in the 1910s and clarified the purpose of its disposal.