• 한국환경복원기술학회지
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• 제6권6호
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• pp.86-95
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• 2003

The object of this paper is to correct check the tree situation and quantity around highway. Also, those data utilize in order to establish plan about how to the long and short term landscape construction and maintain program. The result of this study can be summarized as follows; 1. Tree decrease rates for 8 branch offices were Jongbu(5.62%), Gangwon(4.32%), Chungcheong (3.35%), Honam(5.62%), Gyeongbuk(3.06%), Gyeongnam(5.60%), Seorak training center(0.31%), Headquarter(1.54%). Also decrease causes were traffic accidents(1.8%), air po11ution(4.7%), humid damage(0.9%), insect and disease(1.2%), wind and rainfall(3.4%), dry damage(3.5%), cold damage (1.0%), fire(3.1%), damage of the man and anima1(4.1%), remove bad tree(13.1%), bad rooting(9.5%) and etc.(53.7%). 2. Improve methods of tree death problems were regulation management(ferti1ize, irrigation and pesticide work), improvement of draining system, Pull out the weeds, Plant native plants, utilize organic matter fertilize and plant environment trees.

• 한국안전학회지
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• 제35권1호
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• pp.97-106
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• 2020

The objective of this paper is to suggest a new quantification method for multi-unit probabilistic safety assessment (PSA) that removes the overestimation error caused by the existing delete-term approximation (DTA) based quantification method. So far, for the actual plant PSA model quantification, a fault tree with negates have been solved by the DTA method. It is well known that the DTA method induces overestimated core damage frequency (CDF) of nuclear power plant (NPP). If a PSA fault tree has negates and non-rare events, the overestimation in CDF drastically increases. Since multi-unit seismic PSA model has plant level negates and many non-rare events in the fault tree, it should be very carefully quantified in order to avoid CDF overestimation. Multi-unit PSA fault tree has normal gates and negates that represent each NPP status. The NPP status means core damage or non-core damage state of individual NPPs. The non-core damage state of a NPP is modeled in the fault tree by using a negate (a NOT gate). Authors reviewed and compared (1) quantification methods that generate exact or approximate Boolean solutions from a fault tree, (2) DTA method generating approximate Boolean solution by solving negates in a fault tree, and (3) probability calculation methods from the Boolean solutions generated by exact quantification methods or DTA method. Based on the review and comparison, a new intersection removal by probability (IRBP) method is suggested in this study for the multi-unit PSA. If the IRBP method is adopted, multi-unit PSA fault tree can be quantified without the overestimation error that is caused by the direct application of DTA method. That is, the extremely overestimated CDF can be avoided and accurate CDF can be calculated by using the IRBP method. The accuracy of the IRBP method was validated by simple multi-unit PSA models. The necessity of the IRBP method was demonstrated by the actual plant multi-unit seismic PSA models.

• 한국방재학회 논문집
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• 제9권2호
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• pp.39-43
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• 2009

본 연구는 지표화 산불피해지에서 우리나라에 가장 많이 분포하는 소나무, 잣나무, 낙엽송, 리기다소나무, 해송, 삼나무, 참나무류 등 7개 수종의 임목고사율을 조사 분석하였다. 조사결과 임목고사율은 삼나무>잣나무>소나무>해송>낙엽송>리기다소나무>참나무류 순이었다. 또한, 수간피해율이 높을수록 고사율이 높게 나타났고, 흉고직경이 클수록 고사율은 낮은 경향이었다. 특히 참나무류의 경우 수간 및 수관피해율이 30%이하에서는 거의 생존하는 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2092-2098
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• 2024

Probabilistic safety assessment (PSA) plays a critical role in ensuring the safe operation of nuclear power plants. In PSA, event trees are developed to identify accident sequences that could lead to core damage. These event trees are then transformed into a core-damage fault tree, wherein the accident sequences are represented by usual and complemented logic gates representing failed and successful operations of safety systems, respectively. The core damage frequency (CDF) is estimated by calculating the minimal cut sets (MCSs) of the core-damage fault tree. Delete-term approximation (DTA) is commonly employed to approximately solve MCSs representing accident sequence logics from noncoherent core-damage fault trees. However, DTA can lead to an overestimation of CDF, particularly when fault trees contain many nonrare events. To address this issue, the present study introduces a new zero-suppressed ternary decision diagram (ZTDD) algorithm that averts the CDF overestimation caused by DTA. This ZTDD algorithm can optionally calculate MCSs with DTA or prime implicants (PIs) without any approximation from the core-damage fault tree. By calculating PIs, accurate CDF can be calculated. The present study provides a comprehensive explanation of the ZTDD structure, formula of the ZTDD algorithm, ZTDD minimization, probability calculation from ZTDD, strength of the ZTDD algorithm, and ZTDD application results. Results reveal that the ZTDD algorithm is a powerful tool that can quickly and accurately calculate CDF and drastically improve the safety of nuclear power plants.

• 한국환경과학회지
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• 제31권9호
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• pp.735-741
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• 2022

Global warming affects forests and their ecology. Diversity in the forest is a buffer that reduces the damage due to global warming. Mixed forests are ecologically more valuable as versatile habitats and are effective in preventing landslides. In Korea, most forests were created by simple afforestation with trees of evergreen species. Typically, evergreen trees are shallow-rooted, and deciduous trees are deep-rooted. Mixed forest tree roots grip the soil effectively, which reduces the occurrence of landslides. Therefore, improving the distribution of tree types is essential to reduce damage due to global warming. For this improvement, the investigation of tree types of the forest is needed. However, determining the tree type distribution of forests that are spread over wide areas is labor-intensive and time-consuming. This study suggests effective methods for determining the distribution of tree types in a forest that is spread across a relatively wide area. Using normalized difference vegetation index and RGB images from unmanned aerial vehicles, each evergreen and deciduous tree, and grassland area can be distinguished. The distinguished image determines the distribution of tree type. This method is effective compared to directly determining the tree type distribution in the forest by the use of manpower. The data from these methods could be applied to plan a mixed forest or to prepare for future damage due to global warming.

• 한국환경복원기술학회지
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• 제14권2호
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• pp.1-10
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• 2011

Six pine trees (Pinus densiflora S. et Z.) at the Euilimji Lake Park in Jecheon were collected to investigate tree ages, growth decline pattern and the years of death. Tree-ring measurement was carried out using the Lintab with a resolution of 0.01mm. Tree age were 80-176 years. Cross-dating between the tree-ring series of each tree and the local chronology from Worak Mountain resulted that four and two trees died in 1998 and 1999, respectively. Three dead trees had only formed earlywood in the outermost tree ring and the others had incomplete latewood. Therefore, it was proven that the former trees died between spring and early summer, whereas the later ones died during late summer and/or autumn. The simultaneous deaths of trees suggest the insect damage and/or drought may be the crucial reason of the death, but frequent reaction woods, which were formed by leaning stem, and scars formed by physical damage may also contribute to the death.

• 한국조경학회지
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• 제41권1호
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• pp.44-50
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• 2013

조경수 관리시 발생하는 병충해 등의 문제에 대한 자문을 받기 위하여 관리 담당자는 나무병원에 진단 및 처방을 의뢰하고 있는데, 본 연구는 국내에서 수목진단센터로 인증된 서울대학교 식물병원, 충북대학교 식물종합병원 및 강원대학교 수목진단센터의 온라인 상담게시판에 등록된 조경수 관련 질의와 답변을 검토하여 조경관리자 및 관계자들이 주로 질의하는 조경수 관리상의 문제와 의문이 무엇인지 분석하고자 하였다. 그 결과, 질의자 중에 조경관계자가 81.4%로 대다수를 차지했으나, 질의시 조경수 진단에 필수적인 수목관리 이력 및 주변환경 설명을 한 경우가 11.5%에 불과할 정도로 조경관계자들이 수목진단에 관한 기초적 지식이나 관심이 부족함을 확인하였다. 그리고 조경수 관련 질의 263건 중 생리피해 질의가 94건, 35.8%로 가장 많은 건수를 나타냈다. 이어서 충해, 병해 순이었다. 표징이 없고 다양한 스트레스에 의해 발생하는 생리적 문제의 특성상 진단 및 처방의뢰를 가장 많이 하게 되는 것으로 판단된다. 생리피해의 원인으로는 수분스트레스와 온도스트레스가 가장 많은 편이었으며, 병해는 그 병의 종류가 다양하였고, 생리적 원인이 수반되는 복합피해도 많은 편이었다. 충해는 나방류에 의한 경우가 가장 많았다. 이와 같은 결과를 고려할 때, 조경 기술자와 학생이 조경수 관리의 필수 지식과 정보를 습득하고 관심도를 고취할 수 있도록 대학이나 기술자 교육기관에서 조경수 관리교육을 반드시 실시하여야 하며, 특히 수목 생리에 대한 심도있는 학습 기회 제공과 기술자 스스로의 노력이 요구된다. 또한 조경업에 대한 이해와 조경식재 기술 및 현장의 실정을 이해하는 조경식재 및 관리에 대해 전문적으로 자문할 수 있는 기관의 구성이 이루어져야 한다. 그리고 아직 기반이 갖추어지지 않은 조경수 관리분야의 체계성과 전문성 도모를 위해 집중적인 기술자 육성과 학계와 업계 등 관계자들의 연구가 필요하다.

• Wind and Structures
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• 제22권1호
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• pp.89-106
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• 2016

With an aim to assess the wind damage to urban trees in more realistic conditions, the nonlinear dynamics of structured trees subjected to strong winds with different levels is investigated in the present paper. For the logical treatment of dynamical behavior of trees, material nonlinearities of green wood associated with tree biomechanics and geometric nonlinearity of tree configuration are included. Applying simulated fluctuating wind velocity to the numerical model, the dynamical behavior of the structured tree is explored. A comparative study against the linear dynamics analysis usually involved in the previous researches is carried out. The failure wind velocity of urban trees is then defined, whereby the failure percentages of the tree components are exposed. Numerical investigations reveal that the nonlinear dynamics analysis of urban trees results in a more accurate solution of wind-induced response than the classical linear dynamics analysis, where the nonlinear effect of the tree behavior gives rise to be strengthened as increasing of the levels of wind velocity, i.e., the amplitude of 10-min mean wind velocity. The study of relationship between the failure percentage and the failure wind velocity provides a new perspective towards the vulnerability assessment of urban trees likely to fail due to wind actions, which is potential to link with the practical engineering.

• 한국응용곤충학회지
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• 제47권2호
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• pp.127-131
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• 2008

참나무시들음병의 매개충인 광릉긴나무좀, Platypus koryoensis(Murayama)은 한국에서 참나무시들음병원균인 Raffaelea sp.를 매개하는 것으로 알려져 있다. 참나무시들음 발병정도는 광릉긴나무좀의 밀도에 의존적인 것으로 추정되고 있다. 이에 (樹幹)내 천공수와 집중도가 참나무 피해정도에 미치는 영향을 구명하기 위하여 본 연구를 수행하였다. 수락산 피해지에서 고사목 6그루와 피해목 28그루의 신갈나무의 피해정도, 단위면적당 천공수, 천공간 최근거리를 수간의 상부(지표로부터 50cm)와 하부(지표면)에서 조사하였다. 상부와 하부에서의 천공수는 양의 상관을 보였으며 천공간 최근거리 또한 같은 경향을 보였다. 천공수가 증가할수록 수목의 피해도가 심하였으나 수목의 피해도가 심할수록 천공간 최근거리는 감소하였다. 천공의 분포도 수목의 피해도가 증가할수록 집중분포에서 군일분포로 바뀌었다. 광릉긴나무좀이 초기에는 집중적으로 공격을 하나 수간내 밀도가 증가함에 따라 종내경쟁이 일어나고 경쟁의 결과 개체간 간섭현상이 유도되고 천공의 공간적 분포가 균일하게 변환하게 된다는 것을 암시하는 것이다.

• Journal of Ecology and Environment
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• 제43권4호
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• pp.364-375
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• 2019

Background: Ecologists continue to investigate the factors that potentially affect the pattern and magnitude of tree damage during catastrophic windstorms in forests. However, there still is a paucity of research on which trees are more vulnerable to direct damage by winds rather than being knocked down by the fall of another tree. We evaluated this question in a mixed hardwood-softwood forest within the Big Thicket National Preserve (BTNP) of southeast Texas, USA, which was substantially impacted by Hurricane Rita in September 2005. Results: We showed that multiple factors, including tree height, shade-tolerance, height-to-diameter ratio, and neighborhood density (i.e., pre-Rita stem distribution) significantly explained the susceptibility of trees to direct storm damage. We also found that no single factor had pervasive importance over the others and, instead, that all factors were tightly intertwined in a complex way, such that they often complemented each other, and that they contributed simultaneously to the overall susceptibility to and patterns of windstorm damage in the BTNP. Conclusions: Directly damaged trees greatly influence the forest by causing secondary damage to other trees. We propose that directly and indirectly damaged (or susceptible) trees should be considered separately when assessing or predicting the impact of windstorms on a forest ecosystem; to better predict the pathways of community structure reorganization and guide forest management and conservation practices. Forest managers are recommended to adopt a holistic view that considers and combines various components of the forest ecosystem when establishing strategies for mitigating the impact of catastrophic winds.