• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.897-904
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• 2022

Sports video is a very critical information resource. High-precision extraction of effective segments in sports video can better assist coaches in analyzing the player's actions in the video, and enable users to more intuitively appreciate the player's hitting action. Aiming at the shortcomings of the current sports video clip extraction results, such as strong subjectivity, large workload and low efficiency, a classification method of sports video clips based on MobileNetV3 is proposed to save user time. Experiments evaluate the effectiveness of effective segment extraction. Among the extracted segments, the effective proportion is 97.0%, indicating that the effective segment extraction results are good, and it can lay the foundation for the construction of the subsequent badminton action metadata video dataset.

• Journal of the Korean Geotechnical Society
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• v.32 no.8
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• pp.5-14
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• 2016

The leakage of water under sewer pipelines is one of main sources of sinkholes in urban areas. We performed laboratory model tests to investigate the presence of cavities using impact-echo method, which is a nondestructive test method. To simulate a concrete sewer pipe, a thin concrete plate was built and placed over container filled with sand. The cavity was modeled as an extruded polystyrene foam box. Two sets of tests were performed, one over sand and the other on cavity. A new impact device was developed to apply a consistent high frequency impact load on the concrete plate, thereby increasing the reliability of the test procedure. The frequency and transient characteristics of the measured reflected waveforms were analyzed via fast Fourier transform and short time Fourier spectrum. It was shown that the shapes of Fourier spectra are very similar to one another, and therefore cannot be used to predict the presence of cavity. A new index, termed resonance duration, is defined to record the time of vibration exceeding a prescribed intensity. The results showed that the resonance duration is a more effective parameter for predicting the presence of a cavity. A value of the resonance period was proposed to estimate the presence of cavity. Further studies using various soil types and field tests are warranted to validate the proposed approach.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.61-69
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• 2021

In this study, scale down model bridge piers were fabricated and non-destructive experiments conducted with an impact load to determine scours in the ground adjacent to the bridge piers using the natural frequency of the bridge piers. Three scale-model bridge piers with different heights were fabricated, and they penetrated the ground at a depth of 0.35 m. The scours around the bridge piers were simulated as a side scour and foundation scour. The experiments were conducted in 13 steps, in which scouring around the model bridge piers was performed in 0.05 m excavation units. To derive the natural frequency, the impact load was measured with three accelerometers attached to the model bridge piers. The impact load was applied with an impact hammer, and the top of the model bridge pier was struck perpendicularly to the bridge axis. The natural frequency according to the scour progress was calculated with a fast Fourier transform. The results demonstrated that the natural frequency of each bridge pier tended to decrease with scour progress. The natural frequency also decreased with increasing pier height. With scour progress, a side scour occurred at 70% or higher of the initial natural frequency, and a foundation scour occurred at less than 70%.

• Korean Journal of Legislative Studies
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• v.25 no.3
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• pp.69-96
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• 2019

This paper is written to suggest several recommendations for South Korea to deter and defend North Korean nuclear threat, when North Korea does not seem to give up its nuclear weapons and the US's extended deterrence including the nuclear umbrella could remain uncertain. For this purpose, it explains key options regarding nuclear deterrence and defense by non-nuclear weapon state. It evaluates the current status of South Korean non-nuclear preparedness against North Korean nuclear threat and provides some recommendations to improve the preparedness. As a result, this paper concluded that South Korean non-nuclear preparedness against North Korean nuclear threat was not that reliable. The preparedness has weakened since the South Korean effort to denuclearize North Korea through negotiations in 2018. In this sense, South Korea could have serious problems in protecting its people from North Korean nuclear threat if the US promise of extended deterrence is not implemented. South Korea should focus on its decapitation operation to North Korean highest leaders in case of North Korean nuclear attack based on a minimal deterrence concept. It should be prepared to conduct preventive strikes instead of preemptive strikes due to North Korea's development of solid fuel ballistic missiles. It should integrate its Ballistic Missile Defense with that of the US forces in Korea. South Korea should make a sincere effort for nuclear civil defense including construction of nuclear shelters.

• Journal of the Korean GEO-environmental Society
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• v.1 no.1
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• pp.71-78
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• 2000

In this study, the evaluation for effective utilization of waste landfill was performed by field test to use waste landfill as construction site(Nangido in Seoul). This site had been formed by dredging the household waste, building debris and industrial waste for fifteen years(78'3~93'3). The site where dynamic compaction test was divided by 4 yards. Yard-1, 2 were not eliminated widening of cover soil and Yard-3, 4 were eliminated it. Dynamic Compaction Pilot Test was carried out by the 15ton heavy tamper with drop height of 20m in Yard-1, 3 and with drop height of 15m in Yard-2, 4. We evaluated the compaction efficiency, optimum compaction number and noise vibration through field test, monitoring. As a result, if the countermeasures against vibration and noise by the method utilize, the dynamic compaction method is suitable for using in waste landfill as a construction site among the ground improvement method.

• Journal of Digital Contents Society
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• v.16 no.3
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• pp.417-424
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• 2015

The research of occupational injury for safety and health is a comparatively recent occurrence. As labor activities took place regarding to employee concerns in industrial uprising, human resources health was tried to enhanced as a labor safety subject. Noticing that traditional statistics approach has limitations in learning future forecasting and major factors causing occupational injuries in each industry, Korean Government initiated a quantitative systematic simulation model project to analyze how the annual injury rate has been dropped and stays in a level for recent years. From this motivation and the project, system dynamics models have been developed to explain the mechanisms for reducing annual injury rate, and the mechanisms quantitatively. The main cause effects for the reduction of annual injury rate were due to the government driven investment on safety facilities. In overall viewpoint the gain achievable from these efforts has been reached a saturated level. However, it could reduce the annual injury rate if you chose the industry and size carefully. The model for forecasting, major injury factors, safety budget and allocation are introduced and analyzed, and Analyzing occupational injury related factors can also reduce employee injury and disease related costs, including medical care, quit, and disability assistance costs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4863-4873
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• 2014

The Korean construction industry has played a major role among all industries despite its relative small ratio of all. The global economic crisis, however, has adversely affected the construction industry. Therefore, the Korean government implemented a corporate restructuring process to ensure the stability of the financial market. The selection standard on workout enterprises by the government is based on two perspectives: (1) external factors, including macroeconomic indices and (2) internal factors, including financial statements of private enterprises. On the other hand, if considering the characteristics of the construction industry, a certain construction company may not be evaluated only by its financial statements. In other words, a valuation process that utilizes the financial statements only can be concluded to be irrational. Accordingly, this study aims to provide the valuation model, which embraces the characteristics of workout firms, and determines their implications. To accomplish this, each enterprise valuation was measured using DCF and Black Scholes models, and by comparing such results with their market value, each enterprise was determined to be either under or over-valued. The results of this study verified that the valuations of 2 workout companies (out of 4) showed a higher value than the market value.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.115-131
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• 2018

Extension plate attached PHC piles and bolts spliced PHC piles were installed in field test site. Pile integrities were checked during installation with dynamic pile test and the actual pile conditions after installation were compared with integrity index (${\beta}$ index) by PDA test. Theoretically the break in near pile end or pile end (especially extension plate itself) was very difficult to access by integrity index (${\beta}$ index) and also require a high level of knowledge and field experience on PDA test. First actual wave equation of bolts spliced PHC piles due to bolts spliced equipment can be different with welding spliced. Second wave length of the stress wave from installing can be longer than the height of bolts spliced equipment (about 100 mm). Third Beta processing in PDA analysis function is very difficult to access without a high level of knowledge and field experience on wave equation. Above-mentioned three reasons can make conclusion that traditional PDA test in domestic site can not access the integrity of bolts spliced equipment in bolts spliced PHC piles.

• Journal of the Korean GEO-environmental Society
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• v.16 no.2
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• pp.45-52
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• 2015

To minimize the cost of maintenance, repair and over-design of track substructure, an accurate evaluation of strength and stiffness of the track substructure is necessary. In this study, a cone penetrometer with impact penetration rod (CPI) is developed for the evaluation of track substructure. For applicability test, the chamber and field tests were performed. As the experimental results of the CPI, dynamic cone penetration endex (DCPI), cone tip resistance ($q_c$), friction resistance ($f_s$) and friction ratio (Fr) were obtained. In the chamber test, the experimental results show reasonable values for the simulated track substructure. In the field test, the CPI clearly detects the interface between the ballast and the subgrade. Also, discontinuous layers are detected in the subgrade. It is expected that the developed CPI may be an effective tool for the evaluation of track substructure by evaluating the ballast layer by dynamic penetration and the subgrade by static penetration of the inner rod.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.1
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• pp.3-12
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• 2006

The purpose of this study is to describe the Non-Destructive Testing(NDT) of the rockbolt and investigate the applicability of the NDT methods to estimate the integrity of the rockbolt. To examine the rockbolt integrity including rockbolt itself and grouting material, two methods are adopted: numerical and experimental methods. In the numerical method, the numerical code DISPERSE is used to analyze the dispersion of the rockbolt. The dispersion curve shows the effects of the thickness and stiffness of grouted materials on the embedded rockbolt. Therefore, the optimal frequency for the integrity test of the rockbolt is obtained: 20~120kHz in L(1,0) mode. In the experimental methods, destructive and non-destructive tests are carried out in a laboratory. In the non-destructive test, the low frequency mode generated by an impact and t he high frequency mode generated by an ultrasonic transducer seem to characterize the rockbolt condition readily. The experimental results show that the guided waves attenuate more significantly when the stiffness of the grouted material increases and/or the zone of the defect increases. Meanwhile, the ultimate capacity of rockbolt was evaluated through the pull-out tests and is compared to the NDT results. This study demonstrates that the NDT is a valuable tool for the rockbolt integrity evaluation.