• Journal of Power System Engineering
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• v.14 no.5
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• pp.36-40
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• 2010

The ultrasonic guided wave propagates along with the given structure's wall direction. Because of this specific character, the ultrasonic guided waves arc used in many other fields. Especially, it can be readily utilized for nondestructive inspection of various structures that are made up of gas pipes, heat exchanger tubes, and thin plates. Further, the guided wave technology can be readily utilized when inspecting pipes or thin plates which pose high risk of the accident but for which the nondestructive inspection itself is impossible because it is difficult to get to them since they are coated or buried underground. In the other hand, conventional ultrasonic testing such as thickness gauging uses bulk waves and only tests the region of structure immediately below the transducer. As a result of the application about inlet and outlet cooling water line using guided wave test, we conformed that the overall corrosions were in the lower side of the 304.8 mm inlet valve and these corrosions were engaged in not locally but through the lower side of the valve line. In the near future, we can expect that the detectable defect size is smaller than before along with the development of the sensing technology.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.624-629
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• 2014

The purpose of this study is to carry out the task of engine hesitation which occurred intermittently in driving due to the defective CKPS of LPI vehicles. As the result of the wrong data from the equipment of D-logger, the signal error of CKPS caused the engine hesitation. We performed a study in the followings to analyze and investigate the cause effectively. First, we have investigated the control wiring harness and connector pin contact defect inspection. Second, we have inspected the defection of CKPS separately. From this study, it was found that the engine hesitation were caused by the bad durability and we have showed how to diagnosis the fault of the engine hesitation intermittently while driving. Therefore, it is determined that we have to improve the durability of the CKPS through a strict quality control and to increase the reliability.

• Journal of the Korea Safety Management & Science
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• v.19 no.1
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• pp.15-25
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• 2017

The findings were summarized as follows. The safety check by manufacturer showed that 6 of 13 companies are over the average occurrence of defects. It was expected that there would be a difference between manufacturing technology capability and production system of each manufacturer. Consequently, manufacturers should institutionally improve and strengthen certification items for the upward standardization of safety certification before factory. Second, the safety check by year showed that the results of this study accord with those of previous studies on defect time. Consequently, manufacturers should classify the 3-year-old equipment for vehicle-mounted MEWP into a special check subject to do a nondestructive test according to proven results, and also reflect the test in a safety test system to do regular preventive activities of equipment defects. Third, the safety check by part showed that the boom and outrigger parts of vehicle-mounted MEWP have the most defects. Stress concentration resulted in defects as the boom part was most frequently operated in the structural parts for a real work. To prevent this, it is suitable to improve the hardness of boom materials. The outrigger part needs improvement in safety devices with materials. As an outrigger supports the overturning moment of equipment, it is most affected by its load based on the operating radius, resulting in fatigue crack.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.421-431
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• 2009

This paper is the study on the verification of structural health monitoring (SHM) algorithm based on the ultrasonic guided wave. An active inspection system using Lamb wave (LW) for SHM was considered. The basic study about the application of this algorithm was performed for detecting the circular notch defect in steel plate. LW testing technique, pitch-catch method, was used for interpretation of circular notch defect with depth of 50% of plate thickness and 7 mm width. Damage characterization takes place by comparing $S_0$ mode sensor signals collected before and after the damage event. By subtracting the signals of both conditions from each other, a scatter signal is produced which can be used for damage localization. The continuous Gabor wavelet transform is used to attain the time between the arrivals of the scatter and sensor signals. A new practical damage monitoring algorithm, based on damage monitoring polygon and pitch-catch method, has been proposed and verified with good accuracy. The possible damage location can be estimated by the average on calculated location points and the damage extent by the standard deviation.

• The Journal of the Korea Contents Association
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• v.4 no.2
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• pp.50-60
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• 2004

Recently, most of the embedded system is required not only many functions but also real-time characteristics in purpose. In the hard real-time system, especially, strict deadline of periodic task can affect the performance of the system. In this paper, we design and implement the scheduler based on RM(Rate-Monotonic) rule. This scheduler makes feasible patterns based on EDF(Earliest deadline first) rule with extended schedulability inspection before execution, for periodic task-set that has high CPU utilization and then, execute periodic task-set depended on feasible patterns. The feasible pattern formed into EDF rule is capable of the efficiency of CPU up to 100 percentage and by the referenced execution of the feasible pattern is possible of removing the red-time scheduling overhead that is the defect of the order of dynamic assignment rule.

• Journal of Korean Society of Archives and Records Management
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• v.20 no.3
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• pp.1-21
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• 2020

Although the National Archives of Korea has been receiving transfer of standard electronic documents with a retention period of more than 30 years from the central administration since 2015, errors and inefficiencies persist. Despite this, however, there remain no studies that analyze or address these issues. This study aims to bridge this gap and found that most errors in the transfer process occur at the production stage. To address such, this study proposes a four-step solution. First, before electronic document approval, the text and attached files are checked for defects to prevent errors. Second, as soon as the signature is made, digital signatures are applied on a file-by-file basis to ensure integrity. Third, integrity verification and transfer inspection are automatically performed through digital signature investigation and defect check procedure during transfer and preservation. Fourth and last, the criteria of acquiring records and integrity guarantee technologies are properly applied in production stage with proper management and supervision.

• Journal of the Korean Institute of Navigation
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• v.17 no.3
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• pp.57-68
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• 1993

The economy of Korea has grown up significantly in its scale. It has, therefore, become imperative to develop countermeasures to prevent work related injuries and occupational illnesses resultining from haza-rdous working conditions and handling harmful substances. A lot of cargo handling accident in port have occurred due to the characteristics of poor working environment, diversity of working place and method, fluctuation of the amount of cargo and handling of heavy, long, harmful and dangerous cargo, etc. According to '91 industrial accident analysis carried out by the ministry of labour, the number of the stevedores injured by cargo handling accident in port were 1, 432 persons (the death accident : 22 per-sons), the amount of industrial accident compensation in port was 6.7 billion won (the amount of economic loss : 33.6 billion won), and the injury occurance rate of the stevedoring industry was higher than that of the whole industry. This paper, therefore, aims to the actual status of the stevedoring industry and to extract the main cau-ses of the accidents related to cargo handling in port through factor analysis using the data of the accide-nts in the whole habour from 1990 to 1992, and to suggest the countermeasures to prevent such accident. The main causes of the accident and countermeasures are found to be as follows through the factor analy-sis : Factor1, factor2, and factor3 related to a defect of human being and management, a defect of state and environment, and an insufficiency of education and law are extracted. The short-term countermeasures to prevent these accidents are 1) to consolidate the safety and health organization in the working spot, 2) to secure a safe condition in working spot before dock work, 3) to strengthen a dock worker's safety educa-tion. The long-term countermeasures are 1) to promote a decasualisation of dock workers, 2) to modernize the cargo working methods through constructing exclusive pier and introducing exclusive cargo handling equipment, 3) to establish a exclusive dock accident prevention organization and the dock workers law. Factor 4, factor5, factor6, and factor7 related to an unfitness, a deficiency of technical knowledge, a nonfu-lfilment of safety measures, and a bad arrangement are extracted. The countermeasures to prevent these accidents are 1) to perform a complete safety inspection of cargo handling equipments and tools and to carry out the dock work according to a working plan, 2) to publish and supply technical safety books, safety instruction book, safety check list, etc., 3) to strengthen the safety patrol at the working spot in habour and to activate a safety fund, 4) to maintain always a clean workshop with the safety consciousness in which the good arragement of the working spot is considered to be the beginning of safety.

• Korean Journal of Environment and Ecology
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• v.36 no.5
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• pp.535-549
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• 2022

Damage to forests, such as broken or falling trees, has increased due to the increased intensity and frequency of abnormal climate events, such as strong winds and heavy rains. However, it is difficult to respond to them in advance based on prediction since structural defects such as cavities and bumps inside trees are difficult to identify with a visual inspection. Non-invasive sonic tomography (SoT) is a method of estimating internal defects while minimizing physical damage to trees. Although SoT is effective in diagnosing internal defects, its accuracy varies depending on the species. Therefore, it is necessary to analyze the reliability of its measurement results before applying it in the field. In this study, we measured internal defects in wood by cross-applying destructive resistance micro drilling on old Pinus densifloraSiebold & Zucc. and Ginkgo bilobaL., which are representative tree species in Korea, to verify the reliability of SoT and compared the evaluation results. The t-test for the mean values of the defect measurement between the two groups showed no statistically significant difference in pine trees and some difference in ginkgo trees. Linear regression analysis results showed a positive correlation with an increase in defects in SoT images when the defects in the drill resistance graph increased in both species.