• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.50-56
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• 2022

Change Orders generally impact cost and schedule performance of highway projects. However, highway projects that do not have any change orders also face cost growth and schedule delays. This study seeks to determine the cost and schedule performance of Texas DOT projects by collecting project data for 120 highway projects completed between 2016 to 2020. For the study, we selected project data that has zero or negative change orders which were then grouped and analyzed based on their Project Types i.e., maintenance works; structural works; restoration and rehabilitation works; and safety works. The study found that performance of Maintenance and Safety type projects had less cost and schedule growth among the data analyzed. Statistical tests also found that even though the projects have no change orders, Rehabilitation and Restoration type projects experienced significant schedule growth compared to others. However, the data did not show any significant cost and schedule growth for the projects when statistical tests were performed on overall data. The study concluded that highway projects are experiencing schedule growth even though the projects had no change orders. Results from the study can help planners, engineers, and administrators to gain better insight on how different types of highway projects are performing in terms of cost and schedule and eventually derive appropriate solutions to minimize cost and schedule growth in such projects.

• 한국환경복원기술학회지
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• 제11권4호
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• pp.12-23
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• 2008

This study has a purpose of setting applicable ecological environment plan items when establishing city development plan. To achieve this purpose, multiple methods of data gathering, documentary surveys, and questionaries research were used in this study. The main findings of this study can be summarized as follows; 1. The appliance of ecological environment plan is appropriate to apply before the establishment of development plan. 2. The items applicable to ecological environment plan establishment step by step is the following. First, it is necessary to prepare the environment improvement plan and ecology restoration on the stage of assigning the area. Second, on the stage of planning development plan, it is required to set the restoration plan of ecological resources and step by step ecological environment plan. Third, on the stage of plan implementation, it is required to set the maintenance guide on ecological environment. 3. The planning items of ecological environment plan are "geographical features and soil", "water resource", "wind resource", "green resource", "circulation of resource", "usage of nature energy" and "habitats", etc. 4. To apply ecological environment plan to the planning of development, it is necessary to specify the clear concepts and specific plan. 5. This study is limited to select generalized planning items and later on, it is necessary to develop detailed planning contents.

• 한국환경복원기술학회지
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• 제8권2호
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• pp.83-89
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• 2005

The historical changes of seeding work in Japan, the typical slope revegetation method, is possible to divide into five periods as follows; 1) The early period after creation(1927-1948) 2) The spreading period of modern revegetation work with manpower(1947-1958) 3) The spreading period of rapid revegetation technique using exotic grasses with machineries(1959-1985${\dots}$) 4) The spreading period of rapid reforestation technique by fast growing species mainly using leguminous shrub species(1986-1995${\dots}$) 5)The developing period of nature restoration technique using endemic arborous species(1996-) The evaluation basis of vegetated condition after slope seeding has been described to a official guide book, "The Standards of Slope Stabilizing Works" It was mainly revised three times after first edition in 1972, and also the point of evaluation basis changed from the vegetation coverage to the density of woody plant through the 3rd period and the 4th period Recently main purpose of slope seeding has been developing from the erosion protection to the nature restoration in the current of the 5th period, and "The tentative guidelines of slope nature restoration" was announced by The Slope Revegetation Section of Japanese Society of Revegetation Technology in 2004. It was proposed the planning techniques of using suitable seeds/plants based on the preservation level at the real each construction sites Consequently, at present the importance of advanced monitoring methods for vegetation maintenance and plant sociologic survey to evaluate the plant succession is increasing.

• 한국환경복원기술학회지
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• 제22권4호
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• pp.65-80
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• 2019

The Wetland Conservation Plan is used as a tool to set the management direction of wetland protected areas, and which is establishing a plan for the conservation, wise-use, and management based on wetland's condition. This study was conducted to establish a conservation plan considering the functions and management conditions of Upo wetland protected area. To this end, there are analyzed the current issues, plans and implementation status of Upo Wetland Conservation Plans in the past. The management elements to be considered in establishing the Wetland Conservation Plan were selected through prior research analysis and the priority of those elements was identified through the AHP. As a result, it was found that lack of considering the changes and performance evaluation of the existing plans in wetlands, conducting short-term projects related to maintenance original function of wetland, different management methods for wetland protected areas and other adjacent areas, lack of understanding and cooperation by stakeholders, inconsistencies in timing of the Conservation Plan and survey of wetland protected areas. In order to improve the problem, it needs to include the performance evaluation stage of establishing the conservation plan, strengthen cooperation of stakeholders and expertise, continuing of projects for wetlands' maintenance, priority of the project considering the management side, and to adjust the timing of plans to improve data availability.

• 한국환경생태학회지
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• 제26권6호
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• pp.923-933
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• 2012

본 연구는 최근 이용압력이 높은 서울시 초안산근린공원을 대상으로 숲길의 분포와 훼손 실태를 파악하여 향후 도심 내 숲길 정비 방향을 설정하기 위한 목적으로 수행하였다. 초안산근린공원 숲길(25,964m)의 훼손 현황 중 노폭 2m 이상 20.3%, 침식 깊이 30cm 이상 36.3%, 훼손이 심한 형태인 나지침식이나 근계노출, 암석노출 구간 47.0%이었고, 환경피해도 등급 IV 이상이 70.6%로 숲길 훼손이 심각한 상태이었다. 훼손이 심한 숲길 노선은 대부분 주능선을 따라 형성된 주요 숲길과 저지대 급경사 숲길, 주요 숲길과 연결된 샛길이었다. 연구결과에 기초하여 초안산근린공원 숲길의 복원유형을 숲길 확산방지, 숲길 지반안정, 숲길 노면정비, 숲길 폐쇄 후 식생복원, 유지 등 5가지로 구분하였고, 유형별 복원방안을 제안하였다. 숲길 확산방지는 나지가 노출되어 있는 숲길 폭원 확대를 방지하고, 숲길 지반안정은 숲길 내 침식 및 뿌리노출을 방지하며, 숲길 노면정비는 훼손이 심각한 숲길의 노면을 목재데크, 목재계단, 노면 포장 실시 등을 통하여 보호하기 위한 계획을 수립하였다.

• 한국환경복원기술학회지
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• 제26권6호
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• pp.135-154
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• 2023

Urban wetlands provide various ecosystem services and are subject to restoration and creation projects due to their increased value in the context of climate change. However, the vegetation structure of wetlands is sensitive to environmental changes, including artificial disturbances, and requires continuous maintenance. In this study, we conducted a vegetation survey of three wetlands created as part of a project to restore urban degraded natural ecosystems and monitored the quantitative changes in wetland vegetation structure using an unmanned aerial vehicle. The vegetation survey revealed 73 species in Incheon Yeonhui wetland, and the change in vegetation composition based on wetland occurrence frequency was 11.5% on average compared to the 2018 vegetation survey results. The vegetation survey identified 44 species in Busan Igidae wetland, and the proportion of species classified as obligate upland plants was the highest at 48.8% among all plants, while the proportion of naturalized plants accounted for 15.9% of all plants. The open water surface area decreased from 10% in May 2019 to 6.7% in May 2020. Iksan Sorasan wetland was surveyed and 44 species were confirmed, and it was found that the proportion of facultative wetland plant decreased compared to the 2018 vegetation survey results, and the open water surface area increased from 0.4% in May 2019 to 4.1% in May 2020. The results of this study showed that wetlands with low artificial management intensity exhibited a tendency for stabilization of vegetation structure, with a decrease in the proportion of plants with high wetland occurrence frequency and a relatively small number of new species. Wetlands with high artificial management intensity required specific management, as they had a large change in vegetation structure and a partially high possibility of new invasion. We reaffirmed the importance of continuous monitoring of vegetation communities and infrastructure for wetlands considering the function and use of urban wetlands, and restoration stages. These research results suggest the need to establish a sustainable wetland maintenance system through the establishment of long-term maintenance goals and monitoring methods that consider the environmental conditions and vegetation composition of wetlands.

• 한국환경복원기술학회지
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• 제15권5호
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• pp.1-17
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• 2012

This study sought to discover new directions for management and operation national urban parks in Korea by analyzing the reality of the national government parks of Japan where these parks are already well established and managed. In the case of a Japanese national government park, its supporting system was established after the park was built. The means of management also shifted their direction from putting more priority to the administrative body to the residents. The management practices are changing process of its character with focus on residents as the main entity of activity from their existing position of participants. In other words, the national government parks of Japan are going beyond the previous practice of providing maintenance activities to providing experience, interpretation functions to these activities. Especially, they were establishing local networks to plan and execute programs in collaboration with the park management and NPOs. However, they fall short of tangible outcomes despite their continuous efforts to expand the community involvement and reduce the cost in maintenance. To facilitate the effective management of the urban parks in Korea in the near future, much thought needs to go into the management practices ensuring conservation of resources in the land of Korea, as well as people's use of recreation, community revitalization, and development and transfer of advanced technology to provide appropriate preparations to create urban parks in Korea.

• 한국습지학회지
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• 제16권2호
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• pp.213-220
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• 2014

최근 하천정비는 환경에 대한 인식이 높아지면서 이수 및 치수뿐만 아니라 하천환경에 대한 관심이 증가하는 쪽으로 바뀌어가고 있는 실정이다. 따라서, 하천환경 또는 하천복원이 하천사업의 핵심이 되고 있다. 우리나라의 경우, 대부분의 하천이 치수목적의 하천정비에 의해 홍수조절과 주운을 돕기 위해 직강화 되었다. 하도를 직강화 할 경우 안정성 유지가 중요하므로 하천을 따라 제방이 축조된다. 이와같이 이수와 치수를 목적으로 하천에 축조된 댐, 보, 제방 및 수문 등과 같은 구조물의 경우, 하천의 종 횡적 연결성(Connectivity)을 저해하는 요인이 된다. 연결성이란 어떤 서식처에서 다른 서식처로 에너지와 물질을 이동시키거나 자연적인 수로를 통하여 서식처 간을 물리적으로 연결하는 동적인 자연통로로써 장기적인 하천복원관점에서 볼 때 연결성 증대는 유역 내 건강한 생태계 조성을 위해 매우 중요하다. 본 연구에서는 횡적 연결성 회복을 통한 하천복원의 첫 번째 단계로써 연결성에 대한 기본개념을 설명하고 대상유역을 선정하여 연결성을 저해하는 격리, 차단 공간의 유무에 따른 유역 내 흐름양상의 변화를 수치모의 하였다. 본 연구의 결과는 유역 내 수리수문연결기술 개발로 이어질 수 있을 것으로 판단되며, 차후 하천복원사업에 기여할 수 있을 것으로 판단된다.

• Environmental Engineering Research
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• 제19권2호
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• pp.117-122
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• 2014

Indexes of safety, restoration, damage impact, and management reliability were developed to assess reliability of drinking water distribution networks (DWDNs) management. The developed indexes were applied to evaluate the reliability of the pipeline management stage during unexpected mechanical and hydraulic accidents of components. The results were used to support the decision-making process in effective management and maintenance by enhancing the administrator's system understanding and by helping to create appropriate maintenance and management policies. The results of this study indicated that application of a management reliability index to assess DWDNs reliability may help create a more effective plan for establishing DWDNs management and maintenance.

• International Journal of Reliability and Applications
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• 제1권1호
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• pp.15-26
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• 2000

This paper considers an aperiodic preventive maintenance (PM) model for repairable systems, in which the time intervals between two consecutive preventive maintenances are unequal. To propose such an aperiodic PM model, we assume that each PM reduces the current hazard rate by a certain amount which depends on the number of PMs performed previously. If the system fails between PMs, the minimal repair is performed and the hazard rate remains unchanged after the repair. We give the exact expressions for the hazard rate function for the aperiodic PM model. Based on the proposed aperiodic PM model, we suggest the maximum likelihood method to estimate the parameters characterizing the model and apply the method to the case of Weibull distribution. Numerical examples for estimating the parameters are presented for the purpose of illustration.