• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.211-218
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• 2021

This paper addressed the problems of controlling the coupled pitch-roll motions in a marine vessel exposed to the regular waves in the longitudinal and transversal directions. Stabilization of the pitch and roll motions can be regarded as the essential task to ensure the safety of a ship's navigation. One of the important features in the pitch-roll motions is the resonance phenomena, which result in unexpected large responses in terms of pitch and roll modes in some specific conditions. Besides, owing to its inherent characteristics of coupled combination and nonlinearity of restoring terms, the vessel shows various dynamical behaviors according to the system parameters, especially in the pitch responses. Above all, it can be seen that suppression of pitch rate remains the most significant challenge to overcome for ship maneuvering safety studies. To secure the stable upright condition, a quasi-sliding mode control scheme is employed to reduce the undesirable pitch and roll responses as well as chattering elimination. The Lyapunov theory is adopted to guarantee the closed stability of the pitch-roll system. Numerical simulations demonstrate the effectiveness of the control scheme. Finally, the control goals of state convergences and chattering reduction are effectively realized through the proposed control synthesis.

• Journal of the Korean Geotechnical Society
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• v.39 no.2
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• pp.19-30
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• 2023

Underground structures, such as compacted sand piles applied as soft ground countermeasures, are analyzed for settlement and stability by the composite ground design method. The basic principle of the composite ground design method is the arching effect. The reinforcing effect of the pile is evaluated as the stress-distribution ratio. When applying grouting piles with elastic properties using the ground reinforcement method, the existing stress-distribution ratio was only considered when the pile was installed. This study shows that the method of applying the stress-distribution ratio applied in previous studies should be changed when the ground reinforcement pile is installed at an arbitrary location in the ground without raising it to the ground surface. When high strength jet routing is applied, the stress-distribution ratio (n) to the in-situ ground generally ranges from 30 to 50. However, if the pile is located far from the surface and the depth goes down to the boundary depth of the stress sphere, the stress-distribution effect rapidly decreases, and the stress-distribution ratio converges to 1.5.

• Journal of the Korean Society for Library and Information Science
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• v.57 no.1
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• pp.285-308
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• 2023

This study was carried out to survey and analyze the actual state of reading in Goyang citizens, and to utilize it as a base data for Goyang City's 2nd 'Reading Culture Promotion Plan'. To do this, including references related to reading survey and the 2021 National Reading Survey questionnaire survey questions, the questionnaires that reflected characteristics of adult and student respondents constructed. Then, the survey of 960 adults and 540 students in Goyang City conducted and analyzed the results, and several useful suggestions deduced for 'Goyang City Reading Culture Promotion Plan'. First, the category of reading materials have to be expanded from the paper media to the various media. Second, the expandation of collections in libraries and the services that will help actually buy books are necessary. Third, various reading programs should develop, and the opportunities for citizens to participate in reading and club activities through online should also be increased. Fourth, the facilities and service environments for activating reading should ensure that the accessibility of everyday life. Finally, among the existing reading culture promotion projects, the 'smart libraries', 'Inter-library loan services', 'reading and cultural programs management', and 'Goyang Book Pay' projects need to be sustained and expanded. This study is significant in that it has investigated the actual reading situation of real citizens and has converged the opinions necessary for setting the direction of the effective 'Goyang City reading culture promotion plan'.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.111-122
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• 2009

Dissolution of some of geo-materials may yield the loss of the soil strength and the settlement of earth structures. The goal of this study is to monitor the several physical behaviors of soluble mixtures during dissolution. Sand-salt mixtures are used to monitor the meso to macro response including the settlements and shear waves. The mixtures of photoelastic and ice disks are used to monitor micro to meso behavior of soluble mixture including the void ratio, force chain, coordination number and horizontal force changes. In the sand-salt mixtures, shear waves are measured by using bender elements in conventional oedometer cells. In the photoelastic disk - ice disk mixtures, micro to meso response are measured by digital images and load cells. The shear wave velocity decreases at the initial stage of the dissolution, and then increases and approaches to asymptotic value. The larger dissoluble particle and the more random packing produces the severe horizontal fore change. After dissolution, the void increases and the coordination number decreases. This study demonstrates that the particle level behavior such as the changes of the force chain, void ratio, and coordination number affects the global behavior such as the change of the shear wave velocity and horizontal force of the system.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.34 no.2
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• pp.5-31
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• 2023

The purpose of this study is to investigate the current state of reading culture in Gyeongsangnam-do and its infrastructure in order to develop a balanced reading culture in each of the 18 counties of Gyeongsangnam-do, and to come up with plans to promote reading culture in the libraries in the province. To this end, six measures were proposed to revitalize reading culture in Gyeongsangnam-do by reflecting and synthesizing the survey of reading culture infrastructure in Gyeongsangnam-do, the analysis of the reading status of residents of Gyeongsangnam-do, the analysis of the results of the reading culture promotion project in Gyeongsangnam-do Province and the collection of opinions from experts related to the promotion of reading culture in each field. The results of the study are as follows. ① Establishment of Gyeongnam Reading Culture Promotion Governance, ② Establishment of Gyeongnam Reading Culture Promotion Committee and preparation of basis for evaluation roles such as establishment and implementation of reading culture promotion, ③ Creation of specialized collections and preparation of reading culture programs by region, ④ Service between Gyeongnam Representative Library and Gyeongnam Office of Education Systematization of subject and role division, ⑤ Systematization of role division between Gyeongnam representative library and 18 city and county local government libraries, ⑥ Establishment of grounds for reading culture promotion policy of Gyeongnam and 18 city and county local governments, and establishment of cooperation support system based on related laws and regulations.

• Journal of the Korean Society for information Management
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• v.40 no.2
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• pp.1-31
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• 2023

The purpose of this study is to evaluate and analyze the performance of major reading culture promotion projects implemented in Goyang City, in preparation for the establishment of the 2nd Comprehensive Reading Culture Promotion Plan in Goyang City. To achieve this research objective, this study analyzed various literature and statistical data, identified the reading culture environment in Goyang City, and determined whether major projects implemented according to the 1st Comprehensive Reading Culture Promotion Plan established in 2017 were promoted. In addition, a survey was conducted among librarians in Goyang City by constructing a questionnaire to evaluate the promotion performance of actual relevant projects. Then, by aggregating the data on the reading culture environment in Goyang City, the evaluation results of the reading culture promotion projects obtained from the survey among librarians, and the results of the opinions on the reading promotion projects of the reading surveys of Goyang citizens in the previous relevant study, six major policy directions were proposed to be considered in the establishment of the 2nd Comprehensive Reading Culture Promotion Plan in Goyang City.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.21-22
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• 2020

낙동강 하굿둑(이하 하굿둑)은 1987년 부산 사하구와 강서구 사이에 건설되어 하류 지역의 바닷물 유입을 막아 부산, 울산, 경남 등에 안정적으로 생활·농업·공업 등의 분야에 용수를 공급하는 역할을 해왔다. 현재, 하굿둑의 수문은 낙동강 상류로부터 하류로 흘러내려오는 민물(담수)을 방류하기 위해서만 하굿둑 수문을 개방하고 있다. 하구는 하천의 담수와 바다의 염수가 서로 만나는 구역으로 바닷물과 염수의 밀도차에 의한 혼합으로 자연상태의 하구에서는 담수와 염수가 섞이는 기수역이 형성되며, 이러한 특성으로 하구 인근의 지역에서는 일반적인 하천 및 해양, 연안과는 분명히 구별되는 생태계가 조성된다. 하굿둑 건설이후 바닷물(해수)과 민물(담수)이 만나는 낙동강 어귀에 기수생태계가 사라지면서 바닷물이 유입될 수 있도록 하여 생태계를 복원해야 한다는 필요성이 제기되어 왔으며, 하굿둑이 지역에 기여해온 사실은 분명하나 하굿둑으로 인해 생태계 단절이 발생하고 기수생태계가 파괴되었기 때문에 이를 해결하기 위해서는 하굿둑을 개방하여 과거 기수생태계를 복원해야 한다는 목소리가 높아지고 있다. 이에 따라 정부에서는 하굿둑의 기수생태계 복원을 위해서 관계기관 합동으로 의사결정을 하고 효율적인 개방 방안을 모색하는 실무협의회를 구성하여 운영 중이고, 실무협의회 논의를 통해 5개 주요 관계기관(환경부, 국토부, 해양수산부, 부산광역시, K-water) 공동으로 "낙동강하굿둑 운영개선 및 생태복원 방안 연구용역"을 추진 중이다. 2018년 1단계 용역이 완료되었으며, 2019년부터 2단계 연구용역을 추진 중이고 하굿둑 개방의 수준별로 각종 영향을 검토한 후 대책을 마련하여 기수생태계 복원 방안을 수립하는데 그 목적이 있다. 2단계 연구용역에서는 과학적이고 합리적인 기수생태계 복원방안 마련을 위해서 실제로 해수를 유입시키는 3차례의 실증실험 및 수리모형실험 등을 추진한다. 기존 연구들에서도 수문개방에 따른 해수유입 영향에 대해 모델링을 통해서 분석했지만 이는 검증이 이루어지지 않은 결과로 이번 용역에서는 실제 해수를 유입시키고 염분의 침투 및 각종 수생태 영향을 모니터링 한 후 그 결과를 반영하여 모델링을 고도화하고 있다. 최종적으로 고도화된 모델링 결과를 기반으로 기수생태계 조성 방안별로 염분, 수질, 수생태, 침퇴적 등 각종 분야에 대한 정확한 영향을 분석하고 이에 대한 대책을 포함하여 최종적으로 바람직한 기수생태계 복원 방안을 제시할 계획이다. 기수생태계 복원 방안이 계획에만 그치지 않고 실행으로 연결시키기 위해서 필요성에 대한 이해를 바탕으로 공감대를 형성해 나아가고 있으며 지역주민, 전문가, 관계기관 등 민(民)·관(官)·학(學) 다양한 의견을 수렴하여 하구지역내 수량-수질-수생태를 종합적으로 고려하여 복원 방안을 마련 후 사회적인 합의를 추진하여 확정할 예정이며, 하구의 안정적인 관리를 위해 AI 등 4차 산업혁명기술을 적극 적용하는 스마트한 하구물관리(Smart Estuary Watershed Management)"를 활용한 "하구통합물관리" (Estuary Integrated Watershed Management) 등 과학적인 관리를 추진할 계획이다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.193-200
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• 2010

Structural design requires simultaneously to ensure safety by considering quantitatively uncertainties in the applied loadings, material properties and fabrication error and to maximize economical efficiency. As a solution, system reliability-based design optimization (SRBDO), which takes into consideration both uncertainties and economical efficiency, has been extensively researched and numerous attempts have been done to apply it to structural design. Contrary to conventional deterministic optimization, SRBDO involves the evaluation of component and system probabilistic constraints. However, because of the complicated algorithm for calculating component reliability indices and system reliability, excessive computational time is required when the large-scale finite element analysis is involved in evaluating the probabilistic constraints. Accordingly, an algorithm for SRBDO exhibiting improved stability and efficiency needs to be developed for the large-scale problems. In this study, a more stable and efficient SRBDO based on the performance measure approach (PMA) is developed. PMA shows good performance when it is applied to reliability-based design optimization (RBDO) which has only component probabilistic constraints. However, PMA could not be applied to SRBDO because PMA only calculates the probabilistic performance measure for limit state functions and does not evaluate the reliability indices. In order to overcome these difficulties, the decoupled algorithm is proposed where RBDO based on PMA is sequentially performed with updated target component reliability indices until the calculated system reliability index approaches the target system reliability index. Through a mathematical problem and ten-bar truss problem, the proposed method shows better convergence and efficiency than other approaches.

• 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.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.785-796
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• 2023

The adoption of Environmental, Social, and Governance(ESG) practices in domestic construction firms is predominantly driven by major corporations. These companies not only publish reports on their ESG management but also engage in a meticulous process of identifying key issues and setting priorities. This process entails an in-depth evaluation of the severity of various issues and the gathering of insights from experts in the field. Interestingly, a comparative analysis of ESG assessments for construction companies, both domestically and internationally, reveals significant discrepancies in outcomes. These differences stem from the varied evaluation methodologies and criteria employed by different assessing bodies. Addressing this gap, our study proposes a suite of strategies aimed at bolstering ESG management within the construction sector. We advocate for enhanced policy support and financial backing, especially targeting small and medium-sized enterprises(SMEs) to facilitate their engagement in ESG practices. A critical step forward involves the standardization and transparent disclosure of ESG evaluation criteria, tailored to reflect the unique aspects of the construction industry. Moreover, the standardization and publication of ESG assessments for subcontractors are essential, equipping them with the necessary tools for effective ESG management and evaluation. Given the global nature of construction projects, particularly those commissioned by the European Union in regions like Africa and East Asia, adherence to ESG standards is imperative. Our long-term vision includes the development of a comprehensive database detailing ESG regulations and their impacts, segmented by region and country. This repository will serve as a valuable resource for companies venturing into international construction projects.