PURPOSES : When fire event occurs in tunnel the reinforced concrete is exposed to very high temperature at a very short time period. This study investigates the tensile behavior of steel rebar that experienced high temperature. METHODS : The steel rebar was exposed to 200, 400, 600, and 800℃ following the ISO 834 temperature-time fire curve. Hightemperature- exposed steel rebars were tested using the UTM for their yielding and tensile strengths, and elongation rate. RESULTS : Up to an exposure temperature of 600℃, the tensile properties of the rebar did not vary considerably. However, at 800℃ (which corresponds to a temperature rise time of approximately 22 min), the rebar lost its yielding and tensile strength by approximately 27 and 13%, respectively, compared to the control specimen. Further, the elongation rate increased after exposure to 600℃. The above fundamental tensile test results can be a good reference for future guidelines in the repair manual for tunnels after severe fire events. CONCLUSIONS : When steel rebar experiences high temperatures of 800℃, the yield strength of the rebar reduces approximately 27%. This strength reduction can cause severe structural damage to tunnels that use reinforced concrete as the primary structural elements.

This study is to develop a radish skin peeling machine. Currently, radish peeling work is carried out manually, so the unit price is high due to the increase in labor cost, and problems related to hygiene continue to occur. To solve this problem, a field supply type radish skin peeling machine was designed and manufactured. The peeling machine is a principle in which the skin is removed by conveying the radish using a roller and passing through a blade assembly. In this paper, the design and analysis of the roller and blade part applied during the movement of the radish were carried out, and structurally stable results were obtained.

When developing a new motor, a high-speed load test is performed using dynamo equipment to calculate the efficiency of the developed motor using the collected dynamo data. When connecting the test motor and the dynamo used as a load, abnormal noise and vibration may occur in the test equipment rotating at high speed due to misalignment of the connecting shaft and looseness of the connection, which may lead to a safety accident. In this study, three vibration sensors are attached to the surface of bearing parts of the test motor to measure the vibration value, and statistics such as kurtosis, skewness, and percentiles are obtained in order to clearly express the pattern of the measurement data. With these statistics, machine learning models are developed. The developed model in this way can be used as a diagnostic system that can detect abnormal conditions of the motor test equipment through monitoring the motor vibration data during the motor test.

매년 우리나라 연안해역에서 항해 중인 소형선박 및 소형어선과 연안에 어 로작업을 위해 설치된 시설물과의 접촉 사고가 빈번하게 발생한다. 이러한 사 고들은 주로 연안해역에 설치된 양식장, 정치망, 자망 등으로 인해 발생하며,선박 사고의 일반적인 원인으로는 항해 중인 선박에서 선원의 상무인 경계 소 홀, 침로 유지 및 선위 확인의 미충실, 항해 일반원칙과 국제해상충돌방지규칙 의 미준수 등 여러 가지가 될 수 있다. 본 논문에서는 어구손상사고와 관련된 사고의 원인을 검토하기 위해 해양안전심판원 재결서를 통해 분석하였으며, 그 결과 사고의 원인으로 경계 소홀, 설치된 어구와 적절한 거리 미확보, 항해 계 획 수립 미비 등이 사고의 원인으로 작용한 것을 알 수 있었다. 이러한 인적요 인으로 발생하는 사고를 줄이기 위해서는 선원의 꾸준한 안전교육이나 선박 안 전관리체제의 시스템 변경과 같은 오랜 시간과 많은 비용이 필요하다. 본 논문 에서는 어구를 조금 더 빨리 직관적으로 발견하여 인적요소를 제외한 다른 사 고요인을 제거하는 방법으로 사고 발생을 줄일 수 있는 방안을「수산업법」, 「어업면허의 관리 등에 관한 규칙」,「양식장ㆍ어장 표지시설의 설치 기준」, 「양식산업발전법」 등에서 문제점을 파악하고 개선하여 어구손상사고를 줄일 수 있는 방법을 모색해보고자 한다.

해상에서 전복사고가 발생하면 선박이 복원성을 잃고 전복되는 과정에서 승선 하고 있던 선원의 사망․실종․부상 등 인명사고가 발생하는 동시에 전복에 따 른 선체 침수 및 침몰로 인해 선박 소유자는 엄청난 경제적 손실을 입게 된다. 따라서 동일한 전복사고가 발생하는 것을 방지하기 위해서는 현행 선박길이24미터 이상 어선에만 적용되는 복원성검사 및 만재흘수선 표시 규정에 대하 여, 허가받은 어업의 형태와 어구의 종류를 고려하여 총톤수 20톤 미만의 소형 어선으로 확대할 필요가 있다. 또한 기중기 등 조업에 사용하는 중량 어로설비 설치 유무에 따라 추가적인 복원성검사 및 만재흘수선을 표시하고, 사고선박에 대해서는 동일한 사고가 다시 발생하지 않도록 임시검사 규정을 강화하는 등 실질적이고 효과적인 검사 규정이 필요하다. 이에 따라 이 연구에서는 2017년부터 2021년까지 최근 5년간의 해양안전심판 원 재결서를 바탕으로, 자주 발생하고 있는 길이 24미터 미만의 소형어선 전복 사고 발생 원인과 소형어선 검사 규정의 문제점에 관한 연구를 통한 어선검사 규정 개선방안을 모색하였다.

The Ministry of Oceans and Fisheries promoted the installation of eel-ladder for the purpose of creating inland water resources. Currently, eel-ladder have been installed and operated at the Geumgang Estuary Bank (2018), Yeongam Embankment (2019), and Asanman Embankment (2020). In this study, the number of glass eels in eel-ladder in 2021 was monitored and factors affecting the rise that from ocean to river of eels were investigated. Glass eels in eel-ladder were found when the salinity was relatively low, and they started when the freshwater and seawater temperatures were above 20℃. Comparing the number of occurrences by year, the largest number of glass eels was observed in 2021, but it is judged that this is not according to the distribution of glass eels in sea, but rather as a result of the investigator’s eel-ladder repair and guidance on illegal fishing.

In this study, chemically enhanced steam cleaning(CESC) was applied as a novel and efficient method for the control of organic and inorganic fouling in ceramic membrane filtration. The constant filtration regression model and the resistance in series model(RISM) were used to investigate the membrane fouling mechanisms. For total filtration, the coefficient of determination(R2) with an approximate value of 1 was obtained in the intermediate blocking model which is considered as the dominant contamination mechanism. In addition, most of the coefficient values showed similar values and this means that the complex fouling was formed during the filtration period. In the RISM, Rc/Rf increased about 4.37 times in chemically enhanced steam cleaning compared to physical backwashing, which implies that the internal fouling resistance was converted to cake layer resistance, so that the membrane fouling hardly to be removed by physical backwashing could be efficiently removed by chemically enhanced steam cleaning. The results of flux recovery rate showed that high-temperature steam may loosen the structure of the membrane cake layer due to the increase in diffusivity and solubility of chemicals and finally enhance the cleaning effect. As a consequence, it is expected that chemically enhanced steam cleaning can drastically improve the efficiency of membrane filtration process when the characteristics of the foulant are identified.

PURPOSES : The actual service life of repair methods applied to cement concrete pavement is analyzed based on de-icing agent usage. METHODS : Highway PMS data pertaining to de-icing agent usage are classified into three grades: low (1~5 ton/lane/year), medium (5~8 ton/lane/year), and high (greater than 8 ton/lane/year). The repair methods considered include diamond grinding, patching, joint repair, partial depth repair, and asphalt overlay on five major highways. The service life of each repair method is analyzed based on the usage level of the de-icing agent. RESULTS : The service lives of the applied repair methods are much shorter than expected. It is confirmed that the service life afforded by diamond grinding, patching, and joint repair methods are not significantly affected by the use of de-icing agents, whereas that afforded by asphalt overlay and partial depth repair methods is affected significantly. The service life afforded by the asphalt overlay and partial depth repair methods decreases at high usage levels of the de-icing agent (greater than 8 ton/lane/year). CONCLUSIONS : Among the repair methods considered, the service life afforded by partial depth repair and asphalt overlay is affected significantly by the amount of de-icing agent used. Additionally, the differences between the expected and actual analyzed service lives should be considered in the next-generation maintenance strategy for cement concrete pavements.