• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.649-656
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• 2008

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchic void element based on the integrals of Legendre polynomials is used to characterize the fracture behaviour of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of zero stiffness element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem. It is noted that the proposed hierarchical void element can be one of alternatives to analyze the patched crack problems.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.45-52
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• 2009

In conventional structural design, deterministic optimization which satisfies codified constraints is performed to ensure safety and maximize economical efficiency. However, uncertainties are inevitable due to the stochastic nature of structural materials and applied loads. Thus, deterministic optimization without considering these uncertainties could lead to unreliable design. Recently, there has been much research in reliability-based design optimization (RBDO) taking into consideration both the reliability and optimization. RBDO involves the evaluation of probabilistic constraint that can be estimated using the RIA (Reliability Index Approach) and the PMA(Performance Measure Approach). It is generally known that PMA is more stable and efficient than RIA. Despite the significant advancement in PMA, RBDO still requires large computation time for large-scale applications. In this paper, A new reliability-based design optimization (RBDO) method is presented to achieve the more stable and efficient algorithm. The idea of the new method is to integrate a response surface method (RSM) with PMA. For the approximation of a limit state equation, the moving least squares (MLS) method is used. Through a mathematical example and ten-bar truss problem, the proposed method shows better convergence and efficiency than other approaches.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.4
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• pp.158-177
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• 2023

An estuary is a transitional water area that links the land and sea through rivers and streams, transporting various components from the land to the sea, which plays an important role in determining primary productivity in the coastal environment, and this coastal ecosystem captures a huge amount of carbon into biomass, known as blue carbon, which mitigates climate change as a potential carbon reservoir. This study examined the variation of mean grain size and organic carbon content of the surface sediments for 6 years and analyzed their relationship in the western and southern estuarine areas (Han River Estuary, Geum River Estuary, Yeongsan River Estuary, Seomjin River Estuary, and Nakdong River Estuary) and the East Sea upwelling area. During the sampling period (2015 to 2020), seasonal variation of both properties was not observed, because their variations might be controlled by diverse oceanographic environments and hydrographic conditions within each survey area. However, despite the synoptic problem of all samples, the positive relationship was obtained between the averages of mean grain size and organic carbon content, which clearly distinguishes each survey area. The unique positive relationship in all estuarine areas implies that the same process by sediment clay particles is important in the organic carbon accumulation. However, additional important factor may be expected in the organic carbon accumulation in the East Sea upwelling area. Further necessary data (sedimentation rate, dry bulk density etc) should be required for the estimation of carbon stock to evaluate the major estuaries in Korea as potential carbon reservoirs in the coastal environment.

• Journal of Internet of Things and Convergence
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• v.10 no.1
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• pp.39-45
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• 2024

Container volume is a very important factor in accurate evaluation of port performance, and accurate prediction of effective port development and operation strategies is essential. However, it is difficult to improve the accuracy of container volume prediction due to rapid changes in the marine industry. To solve this problem, it is necessary to analyze the impact on port performance using the Internet of Things (IoT) and apply it to improve the competitiveness and efficiency of Busan Port. Therefore, this study aims to develop a prediction model for predicting the future container volume of Busan Port, and through this, focuses on improving port productivity and making improved decision-making by port management agencies. In order to predict port container volume, this study introduced the Extreme Gradient Boosting (XGBoost) technique of a machine learning model. XGBoost stands out of its higher accuracy, faster learning and prediction than other algorithms, preventing overfitting, along with providing Feature Importance. Especially, XGBoost can be used directly for regression predictive modelling, which helps improve the accuracy of the volume prediction model presented in previous studies. Through this, this study can accurately and reliably predict container volume by the proposed method with a 4.3% MAPE (Mean absolute percentage error) value, highlighting its high forecasting accuracy. It is believed that the accuracy of Busan container volume can be increased through the methodology presented in this study.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.133-140
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• 2023

The origin of texts we refer to as literary or artistic may be imagination, but many are based on experiences. In fact, experiences can be the source of artistic imagination since imagination often builds upon experiences. Therefore, the act of verbalizing human experiences using them as raw material can become a great form of art. Transforming past experiences into stories and infusing them with vitality inevitably requires a creative process of reconstruction, which is essentially a literary process. As such, 'Personal Narrative' holds significance as a literary process that weaves facts into stories and shapes them into forms. Individual experiences are stored as personal memories, and these 'personal memories' continuously generate stories. Collections of individual stories are stored as multiple memories, which gradually form 'collective memories' with distinct social and cultural inclinations through the passage of time and invisible yet potent societal and cultural censorship. The problem lies in the fact that individuals may tend to align their own memories with the inclinations of collective memory rather than simply recalling what they personally experienced. In the context of actual history, personal memories and collective memories communicate with each other, producing non-fictional content close to reality and sometimes manifesting as fiction content enriched with imagination. 'Personal Narrative' holds a significant genre as one genre of non-fiction content within our culture.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.269-273
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• 2023

After participating in the Second Boer War in 1899, the Australian Army participated in world wars such as World War I, World War II, the Korean War, and the Vietnam War. To overcome the decline in the social recognition of soldiers and the continuous shortage of troops caused by the protracted war, the status and role of female personnel were expanded. The use of female manpower, which started as medical support during the Second Boer War, expanded to combat support missions such as communications, maintenance, driving, secret document management, and radar surveillance during World War II. After the Vietnam War, the Chiefs of Staff of the Australian Army, Navy and Air Force established a committee to expand women's participation in the military, improved service conditions for female personnel and supplemented regulations so that they were treated as soldiers, not women, and reached a turning point in expanding the role of female personnel in the Australian military. As a result, all combat positions, including special forces, were opened to women in 2014, and a plan was established to increase the proportion of women in each service by 2030. As a result, all combat positions, including special forces, were opened to women in 2014, and the Australian Armed Forces set a plan to increase the proportion of women by 2030. Like the Australian military, South Korea is also experiencing a demographic cliff and shortage of troops due to the continuing low birthrate problem. Through the history and current state of the use of female personnel in the Australian military, we would like to draw implications for the direction our military should go.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.415-419
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• 2023

The New Zealand Defence Force (NZDF) began using female manpower from World War II. After making various efforts to secure excellent manpower, the proportion of female manpower has risen to 24%, higher than that of Britain, the United States, Canada and Australia, which have a longer history of female military personnel than New Zealand. This is the result of NZDF efforts to open combat roles to women and allow female personnel to advance to high-ranking military positions such as generals and consular officers. In addition, policy alternatives to address women's realistic concerns such as pregnancy and childbirth, childcare, and vertical organizational culture were presented. In particular, Operation "Respect" was implemented to overcome the problem of not leaving or joining the army due to inappropriate sexual behavior and bullying. The operation respect established the role of the leader, emphasized the support of the victim, and accumulated data of the accident to prevent similar accidents. In addition, through the "Wāhine Toa" program, excellent female manpower could be introduced into the military through customized support considering the military life cycle (attract-recruit-retain-advance) of female personnel. South Korea is also considering expanding the ratio and role of female manpower as one of the ways to overcome the shortage of troops and leap into an advanced science and technology group. Implications were derived from the use of female manpower in the NZDF and the direction in which the Korean military should proceed was considered.

• Journal of the Korea Society of Computer and Information
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• v.28 no.10
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• pp.1-8
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• 2023

If there is a defect in the wheel bearing, which is a major part of the car, it can cause problems such as traffic accidents. In order to solve this problem, big data is collected and monitoring is conducted to provide early information on the presence or absence of wheel bearing failure and type of failure through predictive diagnosis and management technology. System development is needed. In this paper, to implement such an intelligent wheel hub bearing maintenance system, we develop an embedded system equipped with sensors for monitoring reliability and soundness and algorithms for predictive diagnosis. The algorithm used acquires vibration signals from acceleration sensors installed in wheel bearings and can predict and diagnose failures through big data technology through signal processing techniques, fault frequency analysis, and health characteristic parameter definition. The implemented algorithm applies a stable signal extraction algorithm that can minimize vibration frequency components and maximize vibration components occurring in wheel bearings. In noise removal using a filter, an artificial intelligence-based soundness extraction algorithm is applied, and FFT is applied. The fault frequency was analyzed and the fault was diagnosed by extracting fault characteristic factors. The performance target of this system was over 12,800 ODR, and the target was met through test results.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.795-799
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• 2023

The Canadian military participated in World War I and felt the limitations of the recruitment system through the continuous shortage of troops caused by the prolonged war, therefore expanded the role and scope of female manpower. The use of female manpower, which began with medical support for the first time, increased its necessity and importance as medical support personnel were dispatched overseas and women's manpower was expanded to combat support missions for the Army, Navy, and Air Force. Since then, the proportion of female manpower has been limited to 1.5% of the total number of employees at the end of the Second World War and the reduction of troops and the dismantling of the women's unit. In this situation, the Austrian Defence Force gradually accepts the recommendation of the Royal Canadian Women's Status Committee to improve the service conditions of women, marking a turning point in expanding the role of women in the Canadian military. The the Austrian Defence Force conducted long-term combat experiments to increase the proportion and role of female manpower, increasing reliability through observation and analysis to prove whether female manpower is suitable for combat troops. Korea also wants to draw implications for the future direction by comparing the history and current appearance of the Canadian military's use of female manpower with the Korean military at a time when the problem of a shortage of troops is emerging due to the recent decline in fertility and low birth rates.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.365-370
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• 2023

Royalty contributed to the development of the non-fungible token (NFT) ecosystem as a reward system that pays a portion of the sales to the creator whenever transactions occur. This study quantitatively analyzes the impact of the abolition of royalties, which is being expanded by some NFT marketplaces, on the NFT market, and qualitatively analyzes the results of the impact. The analysis results are as follows. First, the number of NFT mints is decreasing by causing creators to leave the NFT market and reducing new entry. Second, major NFT projects have refused to trade with marketplaces that have abolished royalties, leading to a decrease in the number of transactions. Third, the abolition of royalties has undermined the motivation of NFT creators to continue to develop their projects, leading to a drop in NFT floor prices. This study is expected to contribute to reducing the current negative impact in the short term by suggesting how the NFT community provides incentives to owners who voluntarily pay royalties independently of the policy of the NFT marketplace. In addition, it suggests that in the long run, fundamental solutions to the problem of abolishing royalties require improvements in technology related to royalty payments, cooperation between NFT marketplaces and NFT creators, and institutional support related to royalties.