PURPOSES : This study aims to provide quantitative profile values for the objective evaluation of concrete surface profile (CSP) grades in concrete structures. The main aims are to quantify the CSP grade required for concrete surface pretreatment and proposing a more suitable CSP grade for structural maintenance. METHODS : Initially, the challenges in measuring concrete surface profiles were outlined by analyzing pretreatment work and profile samples of concrete pavements. Theoretical foundations for quantifying concrete surface roughness were established, and regression models including linear regression, cubic regression, and log regression were selected. Additionally, the interquartile range anomaly removal technique was employed to preprocess the data for regression modeling. RESULTS : Concrete CSP profiles were measured through indoor tests, and the measured data were quantified. Linear regression, cubic regression, and log regression models were applied to each CSP grade for comparative analysis of the results. Furthermore, comparative studies were conducted through adhesion strength tests based on the CSP grade. CONCLUSIONS : Our results are expected to establish objective standards for the pretreatment stage of concrete repair and reinforcement. The derived reference values can inform standards for the restoration and reinforcement of concrete structures, thereby contributing to performance improvement. Moreover, our results may serve as primary data for the repair and reinforcement of various concrete structures such as airports, bridges, highways, and buildings.

In this study, infrared thermometry techniques were used to conduct surface wetting performance tests (wicking tests) on micropillar structures with good fluid supply capabilities to enhance the critical heat flux. Wicking tests were conducted based on various micropillar shapes (i.e., diameter and spacing) to investigate the surface wetting performance near the boiling point of the fluid(~100°C). The surface temperature was increased from 20°C to 95°C, to examine the wicking performance The shape of the micropillars were quantified by the roughness and the effect of the roughness and temperature on the wicking performance was analyzed. As a result, we confirmed that the roughness of the micropillars increases the capillary pressure, improving the wicking performance. The sample D04 G10 with the highest roughness coefficient at room temperature (r=2.51) exhibited the highest wicking coefficient, showing a 170% improvement in wicking performance compared to D04G20 with the smallest roughness coefficient at room temperature(r=1.51). Additionally, the D04 G10 sample (r=2.51) recorded a 50% improvement in the wicking coefficient at the highest temperature(95°C) compared to room temperature(20°C). The wicking coefficient data will be utilized as a database for developing a new correlation for critical heat flux.

PURPOSES : The evaluation of the low-temperature performance of an asphalt mixture is crucial for mitigating transverse thermal cracking and preventing traffic accidents on expressways. Engineers in pavement agencies must identify and verify the pavement sections that require urgent management. In early 2000, the research division of the Korea Expressway Corporation developed a three-dimensional (3D) pavement condition monitoring profiler vehicle (3DPM) and an advanced infographic (AIG) highway pavement management system computer program. Owing to these efforts, the management of the entire expressway network has become more precise, effective, and efficient. However, current 3DPM and AIG technologies focus only on the pavement surface and not on the entire pavement layer. Over the years, along with monitoring, further strengthening and verification of the feasibility of current 3DPM and AIG technologies by performing extensive mechanical tests and data analyses have been recommended. METHODS : First, the pavement section that required urgent care was selected using the 3DPM and AIG approaches. Second, asphalt mixture cores were acquired from the specified section, and a low-temperature fracture test, semi- circular bending (SCB) test, was performed. The mechanical parameters, energy-release rate, and fracture toughness were computed and compared. RESULTS : As expected, the asphalt mixture cores acquired from the specified pavement section ( poor condition – bad section) exhibited negative fracture performances compared to the control section (good section). CONCLUSIONS : The current 3DPM and AIG approaches in KEC can successfully evaluate and analyze selected pavement conditions. However, more extensive experimental studies and mathematical analyses are required to further strengthen and upgrade current pavement analysis approaches.

PURPOSES : The objectives of this study are to evaluate the condition of concrete bridge decks using the multi-channel ground penetrating radar (GPR) testing and compare the value of its dielectric constant value with actual concrete condition. METHODS : The reflection coefficient method was used to measure the dielectric properties of concrete bridge decks. Air-coupled step-frequency GPR testing was used to measure the time taken for reflection from the interfaces between the layers. Specimens of the asphalt mixture and concrete bridge-deck were collected by field coring. GPR testing was conducted on two bridges with different concrete bridge deck conditions on national highways. After the GPR tests, the actual conditions of the concrete bridge deck were investigated using specimen coring. RESULTS : GPR testing indicated that the dielectric constants of concrete bridge decks in good condition ranged from 8 to 10, whereas those corresponding to poor condition ranged from 4 to 6. The results of GPR testing can determine the actual condition and degree of distress of concrete bridge decks determined from the specimen coring data. Therefore, GPR testing is appropriate for nondestructively evaluating the condition of a concrete bridge deck. CONCLUSIONS : The analysis results of the dielectric constants of the concrete bridge deck obtained from multichannel GPR testing were consistent with the actual bridge deck conditions. In the near future, an additional verification process for this approach under different bridge conditions will be required to improve its precision and ensure reliability.

As global warming and consumer’s preference for tropical/subtropical fruits increase, the number of orchards cultivating tropical/subtropical fruits in Korea is increasing. Accordingly, concerns about the introduction of exotic invasive pests that host tropical fruits. In this study, efficacy of ethyl formate(EF), as alternative to methyl bromide(MB), was evaluated. Commercial trial of EF was conducted in mango post-harvest storage conditions for controlling Scirtothrips dorsalis. Application of 10 g/m3 of EF for 4 hours at 10 ℃ showed proven efficacy on S. dorsalis without any phytotoxic damage on mango fruits in that condition.

In this study, non-destructive technologies that can be applied to evaluate the integrity of valve materials, safety against internal pressure caused by corrosion, and the blocking function of large-diameter water valves during operation without requiring specimen collection or manpower entering the inside of the valve were tested to assess the reliability of the technologies and their suitability for field application. The results showed that the condition of the graphite structure inside the valve body can be evaluated directly through the optical microscope in the field without specimen collection for large-diameter water butterfly valves, and the depth of corrosion inside the valve body can be determined by array ultrasound and the tensile strength can be measured by instrumented indentation test. The reliability of each of these non-destructive techniques is high, and they can be widely used to evaluate the condition of steel or cast iron pipes that are significantly smaller in thickness than valves. Evaluation of blocking function of the valves with mixed gas showed that it can be detected even when a very low flow rate of mixed gas passes through the disk along with the water flow. Finally, as a result of evaluating the field applicability of non-destructive technologies for three old butterfly valves installed in the US industrial water pipeline, it was found that it is possible to check the material and determine the suitability of large-diameter water valves without taking samples, and to determine the corrosion state and mechanical strength. In addition, it was possible to evaluate safety through the measurement results, and it is judged that the evaluation of the blocking function using mixed gas will help strengthen preventive response in the event of an accident.

Electric doors have been applied in urban trains since 2007 and operated for a long time. Recently, the failure of mechanical devices in electric doors have been increasing. The door is a device that is directly related to the safety of passengers. The rivet breakage of a ball/nut assembly may occur to an accident during train operation. In this study, the operating voltage and acceleration data of the door were collected for rivet condition monitoring, and 4 features were extracted in the frequency domain using the acceleration data. The classification performance of the rivet condition according to the axial direction of the acceleration data and 4 kernel functions was evaluated using SVM algorithm. When the X-axis data and Gaussian kernel function were used, the highest classification performance was shown for the electric door’s rivet with 90% accuracy.

단계별 작업기를 통합하여 일관화하는 복합기를 실용화하여 생산효율이 개선되어 밭농업 생력화에 기여하였다. 본 연구의 목적은 SAS를 이용한 복합작업기의 최적 작업조건을 반응표면기법(RSM)으로 구명하고 최적 성능을 실험으로 평가하여 집약적 밭농업의 트랙터 운용방법을 제시하고자 하였다. 로터리 작업에서 회전속도와 전진속도의 관계는 견인력의 효율성과 멀칭 등 작업품질에 적정한 트랙터의 운용기준 조건을 나타낸다. 슬립과 공차를 고려하면 통합 선택기준 작업속도는 3.4<SPDcr<4.7 km/h 범위로 확장되고, 로터리 피치(p)가 40<p<56 cm/rev로 판단되었다. 여러 검토조건에 서 연료소비량을 예측하고 동력의 효율성을 평가하는데 Kim 모델이 사용되었다. 목적함수를 만족하는 적정 p의 범위에 속하는 공칭 작업속도(SPD)를 엔진속도비(n)와 주행 기어비(GR)로 나타내어 최적 설계점은 카테고리 1급(DK450) 트랙터에 대하여 독립변수 n, GR/변속단수는 0.65, 401/M4로 구명되었다. 실험 평가에서 작은 트랙터는 시뮬레이션과 비교적 일치하였고, 큰 트랙터의 실험은 낮은 연료소비량과 실작업속도로 오차를 유발하였다.

PURPOSES : In this study, a method for evaluating concrete bridge deck deterioration using three-dimensional (3D) ground penetrating radar (GPR) survey data and its in situ application are discussed. METHODS : Field surveys are conducted on two bridges in Yongsan-gu (Bridge A) and Seodaemun-gu (Bridge B) in Seoul using 3D GPR. The obtained survey data are used to calculate the dielectric constant map of each bridge using the extended common midpoint method. In addition, random points on both bridges are selected for the chloride content test in accordance with the KS F 2713 standard. The results from the dielectric constant map and chloride content test are compared. RESULTS : For Bridge A, it is discovered that the percentage of sections with a dielectric constant of 5.0 or less is 1.57%, whereas that above 5.0 is 98.43%; this indicates that the percentage of deteriorated sections for Bridge A is low. Meanwhile, for Bridge B, the dielectric constants calculated for the entire bridge exceed 5.0, which suggests no deterioration for Bridge B. Moreover, all the points selected for the chloride content test have less than 0.15% chloride content and have dielectric constants ranging from 5.0 to 7.0, which are favorable condition for the bridge deck. CONCLUSIONS : The analysis results of the dielectric constants of the concrete bridge deck obtained from the 3D GPR system are consistent with the actual chloride content results. Furthermore, additional verification of this method through field surveys on bridge sections with severe deterioration is highly recommended for future improvements.

생강의 기능성 소재화를 위해 흑생강을 제조함에 있어 숙성 조건 최적화를 위한 숙성 온도(75.0~90.0℃, X1)와 시간(18.0~72.0 hr, X2)을 독립변수로 하고 중심합성계획에 따른 11구간의 조건에서 제조된 흑생강의 이화학적 특성 및 항산화 활성을 측정하였다. 흑생강의 수율은 모든 조건에서 60% 이상이었다. 흑생강의 명도와 황색도, 6-shogaol, 총 페놀 및 플라보노이드 함량은 숙성 온도가 높고 시간이 길어질수록 증가되는 경향이었다. 특히 흑생강의 6-shogaol, 총 페놀 함량 및 항산화 활성은 90℃에서 45 hr 숙성 시 최대값을 보였다. 반응표면분석법에 의한 흑생강의 제조 시 예측된 최적 조건은 89.97℃ 및 21.60 시간이었으며, 실측값은 예측값의 92.7~101.6%의 범위였다.