• Journal of Ecology and Environment
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• 제35권3호
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• pp.235-242
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• 2012

Mikania micrantha, a neo-tropical vine, is spreading rapidly in the tropical part of Nepal and is now threatening the rural ecosystem including biodiversity and rural livelihoods. However, no attempt has been made to control the spread of M. micrantha. As a result, the vines are spreading freely and rapidly. After a thorough literature review and assessment of forest management practices, we proposed a manual cutting method, as it suits the Nepalese situation for several reasons: required labor is readily available, as local communities are managing forest patches, and the method does not have any potential adverse effects on non-target native species. Experimental plots were laid out in August 2011 to examine the effectiveness of manual cutting. Two different site types based on canopy coverage were selected and divided into three blocks based on cutting strategy. Four treatments were assigned across the experimental plots following a complete block design. We harvested above-ground biomass according to the assigned treatment. The results suggested that there should be at least two consecutive cuttings within a 3-week interval before flowering, and that three consecutive cuttings resulted in 91% mortality of the vines. In addition, cutting promoted regeneration of native plant species. Employing regular cutting operations can modify understory shade enhancing regeneration of native species, which is a desirable condition to constrain proliferation of M. micrantha. Periodic cuttings reduced the competitiveness of M. micrantha regardless of canopy openness, but native ground cover should be retained.

• 한국조경학회지
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• 제25권4호
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• pp.171-183
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• 1998

The purpose of this study was to analyze urban greenspace area and vegetation structure by land use types for both Chuncheon and Kangleung. Natural and agricultural lands were predominant in the study cites, as 75-80% of total area. Residential lands accounted for about 10%, and commercial and industrial lands(including transportation), 5-10%. Only 10-20% of urban residential and commercial area was covered with greenspace. Woody plant cover was 12-13%, and tree density was 1.5 trees/100$m^2$ for urban lands(all land use types except natural land) in both cities. The tree-age structure was largely characterized by young, growing tree population, and species diversity within a diameter class decreases as the diameter classes get larger. Urban lands of both cities had quite a similar species composition of woody plants (similarity index of 0.65). Street trees in Chuncheon were intensively pruned annually to protect the above ground utility lines. Some strategies were explored to solve problems found in the existing greenspace structures. They included increase of biomass and greenspace area through minimization of unnecessary impervious surfaces, creation of multilayered and multiaged vegetation structures, relocation of above ground utility lines and avoidance of intensive tree pruning, and establishment of greenspace proximity and connectivity.

• Geomechanics and Engineering
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• 제21권2호
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• pp.171-178
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• 2020

Mountainous areas cover more than 70% of Korea. With the rapid increase in tunnel construction, tunnel-collapse incidents and excessive deformation are occurring more frequently. In addition, longer tunnel structures are being constructed, and geologically weaker ground conditions are increasingly being encountered during the construction process. Tunnels constructed under weak ground conditions exhibit long-term deformation behavior that leads to tunnel instability. This study analyzes the behavior of the bottom region of tunnels under geological conditions of long-term deformation. Long-term deformation causes various types of damage, such as cracks and ridges in the packing part of tunnels, as well as cracks and upheavals in the pavement of tunnels. We observed rapid tunnel over-displacement due to the squeezing of a fault rupture zone after the inflow of a large amount of groundwater. Excessive increments in the support member strength resulted in damage to the support and tunnel bottom. In addition, upward infiltration pressure on the tunnel road was found to cause severe pavement damage. Furthermore, smectite (a highly expandable mineral), chlorite, illite, and hematite, were also observed. Soil samples and rock samples containing clay minerals were found to have greater expansibility than general soil samples. Considering these findings, countermeasures against the deformation of tunnel bottoms are required.

• 한국지반공학회논문집
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• 제27권11호
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• pp.47-54
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• 2011

본 논문에서는 다양한 조건에 대한 터널의 종단변형특성을 분석하여 터널확대 시 종단변형곡선을 제안하였으며 이를 이용하여 최종적으로 프로텍터 보호범위에 대해 고찰해 보았다. 이를 위해 지반물성 및 확대조건별 수치해석을 실시하였으며 터널 확대 조건이 종단변형에 미치는 영향을 파악하여 터널확대 시 적합한 지반종단변형곡선식을 제안하였다. 또한 제안한 종단변형곡선식을 이용하면 2차로 터널을 4차로 확대 시 프로텍터 보호범위는 막장 후방 약 24m, 막장 전방 약 35m를 보호해야 할 것으로 판단된다.

• 한국조경학회지
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• 제26권3호
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• pp.278-287
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• 1998

The halophytes are considered less important in our field, as the land reclamation executed continuously by public or individual. So this research is to use plants more active on the reclaimed land and to verify their utility in the aspect of the landscape planning, design and complementaton. This research is performed at the construction site of Incheon International Airport in Youngjong-do located in West-sea of Korea. Following proposals are the major conclusions drawn from the research:1. The halophytes to be used in the vicinity of the water reservoir in orer to improve the ground for the introduction of new plants and prevent the water contaminatioin. 2. The halophytes to be used as a gound-cover which protects major structures nearby from being damaged by the salt content in the air. 3. Thd halophytes to be used as a unique and panoramic landscape element. They have various colors which change throughout a year. 4. Thd halophytes to be considered as a outdoor recreation resource. The halophytes planted area may be utilized as picnic area, outdoor event plaza, ball game ground, rough in the golf cource and etc. Additional usage of the land include the future rearch site for sea fronted ecological studies and pasture for cows and other livestock.

• Smart Structures and Systems
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• 제23권2호
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• pp.155-171
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• 2019

In this study, Semi-active Tuned Mass Dampers (STMDs) are employed in order to cover the prevailing uncertainties and promote the efficiency of the Tuned Mass Dampers (TMDs) to mitigate undesirable structural vibrations. The damping ratio is determined using type-1 and type-2 Fuzzy Logic Controllers (T1 and T2 FLC) based on the response of the structure. In order to increase the efficiency of the FLC, the output membership functions are optimized using genetic algorithm. The results show that the proposed FLC can reduce the sensitivity of STMD to excitation records. The obtained results indicate the best operation for T1 FLC among the other control systems when the uncertainties are neglected. According to the irrefutable uncertainties, three supplies for these uncertainties such as time delay, sensors measurement noises and the differences between real and software model, are investigated. Considering these uncertainties, the efficiencies of T1 FLC, ground-hook velocity-based, displacement-based and TMD reduce significantly. The reduction rates for these algorithms are 12.66%, 26.43%, 20.98% and 21.77%, respectively. However, due to nonlinear behavior and considering a range of uncertainties in membership functions, T2 FLC with 7.2% reduction has robust performance against uncertainties compared to other controlling systems. Therefore, it can be used in actual applications more confidently.

• Geomechanics and Engineering
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• 제37권4호
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• pp.323-339
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• 2024

If the pressure exerted on the face of a tunnel excavated by TBM exceeds a threshold, it leads to failure of the soil or rock masses ahead of the tunnel face, which results in heaving the ground surface. In the current research, the upper bound method of limit analysis was employed to calculate the blow-out pressure of tunnels excavated in rock masses obeying the Hoek-Brown nonlinear criterion. The results of the proposed method were compared with three-dimensional finite element models, as well as the available methods in the literature. The results show that when σ_ci, m_i, and GSI increase, the blow-out pressure increases as well. By doubling the tunnel diameter, the blow-out pressure reduces up to 54.6%. Also, by doubling the height of the tunnel cover and the surcharge pressure exerted on the ground surface above the tunnel, the blow-out pressure increased up to 74.9% and 5.4%, respectively. With 35% increase in the unit weight of the rock mass surrounding the tunnel, the blow-out pressure increases in the range of 14.8% to 19.6%. The results of the present study were provided in simple design graphs that can easily be used in practical applications in order to obtain the blow-out pressure.

• 대한원격탐사학회지
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• 제30권1호
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• pp.109-126
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• 2014

본 연구에서는 최근(2009-2012)의 MODIS 자료를 이용하여 천리안위성 관측 지역의 지표면 방출률 자료를 개선하였다(KNULSE_v2). 방출률 산출기법은 지표면이 식생과 토양으로만 구성되어 있다는 가정하에 방출률을 계산하는 식생피복법(Vegetation Cover Method)를 이용하였다. 주요 개선 내용은 1) 적설지수를 이용하여 적설에 의한 방출률 변화를 고려한 점, 2) 산출채널을 기존 2개(11, 12 ${\mu}m$)에서 4개(3.7, 8.7, 11, 12 ${\mu}m$)로 확대한 점, 3) 가장 최근의 5가지 지면피복자료를 조합하여 양질의 지면피복분류 자료를 이용한 점, 그리고 4) 최근에 개선된 방출률 조견표를 사용한 점이다. 산출된 자료는 식생이 최대로 성장하는 여름에 비교적 높고 반대로 겨울에 낮은 방출률을 보이며 계절에 따른 변화가 뚜렷하게 나타났다. 반면 사막이나 열대 우림 등 식생의 변화가 크지 않은 곳에서는 계절에 따른 방출률 변동이 매우 적게 나타났다. 눈덮임을 적용함에 따라 3.7, 8.7, 11 ${\mu}m$ 채널에서는 방출률이 증가되었으나 12 ${\mu}m$ 채널에서는 오히려 방출률이 감소되었다. 눈 덮임에 의한 방출률 변동을 고려한 결과 적설시 MODIS LSE와 유사한 방출률 변동패턴을 보였으며, 북반구 고위도에 적설이 존재하는 11월부터 4월까지의 상관관계가 크게 개선되었다(특히 11 ${\mu}m$). 그러나 방출률 차는 상대적으로 증가되었고 특히 3.7 ${\mu}m$ 채널에서 크게 나타났다. 본 연구에서 개선된 자료는 분리대기창 기반의 지표면온도 산출시 기초 입력자료로 사용하여 산출 정확도 향상에 기여할 수 있을 것이다.

• Journal of Forest and Environmental Science
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• 제28권3호
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• pp.158-169
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• 2012

Sabah has experienced a rapid decline in the extent of forest cover. The precise impact of habitat loss on the conservation status of the plants of Sabah is uncertain. In this study we use the niche modelling algorithm MAXENT to construct preliminary, revised and final ecological niche models for Dipterocarpus lamellatus and Dipterocarpus ochraceus and combined these models with data on current land-use to derive conservation assessments for each species. Preliminary models were based on herbarium data alone. Ground surveys were conducted to evaluate the performance of these preliminary models, and a revised niche model was generated from the combined herbarium and ground survey data. The final model was obtained by constraining the predictions of the revised models by filters. The range overlap between the preliminary and revised models was 0.47 for D. lamellatus and 0.39 for D. ochraceus, suggesting poor agreement between them. There was substantial variation in estimates of habitat loss for D. ochraceus, among the preliminary, revised and constrained models, and this has the potential to lead to incorrect threat assessments. From these estimates of habitat loss, the historic distribution and estimates of population size we determine that both species should be classified as Critically Endangered under IUCN Red List guidelines. Our results suggest that ground-truthing of ecological niche models is essential, especially if the models are being used for conservation decision making.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.297-302
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• 2007

Vibrating test of vehicle component can be possible in lab-based simulators instead of field testing owing to the development of technology in control algorithm as well as computational process. Currently, Multi-Axial Simulation Table(MAST) is recommended as a vibrating equipment, which excites a target component for 3-directional translation and rotation motion simultaneously and hence, vibrational condition can be fully approximated to that of real road test. But, the vibration-free performance of target component is not guaranteed with MAST system, which is only simulator subjective to the operator. Rather, the reliability of multi-axial vibration test is dependent on the quality of input profile which should cover the required severity of vibrating condition on target component. In this paper, multi-axial vibration testing methodology of vehicle component is presented here, from data acquisition of vehicle accelerations to the obtaining the input profile of MAST using severe data at proving ground. To compare the severity of vibration condition, between real road test and proving ground one, energy principle of equivalent damage is proposed to calculate energy matrices of acceleration data and then, it is determined the optimal combination of special events on proving ground which is equivalent to real road test at the aspects of vibration fatigue using sequential searching optimal algorithm. To explain the vibration methodology clearly, seat and door component of vehicle are selected as a example.