• Korean Journal of Environment and Ecology
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• v.17 no.4
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• pp.324-336
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• 2004

This study was achieved to present ecological administration plan by analyzing vegetation structure and condition rating class(environmental damage degree) of Sangnim Woods Natural Monument in Hamyang-gun, Korea. In vegetation structure part, actual vegetation was classified by 22 patterns and Quercus serrata Carpinus tschonoskii community(31.8％), Quercus serrata community(14.6％) ranged extensively. Main plant community was 8 types, and is fractionated by 13 plant communities according to stratigraphy development degree it is Quercus serrata community, Quercus serrata Carpinus tschonoskii community, Quercus aliena community, Quercus acutissima community, Carpinus tschonoskii community, Carpinus tschonoskii Quercus serrata community, Zelkova serrata-Quercus serrata community, and Planted area with korean landscape woody plants. Age of old growth trees that diameter of breast height over 38cm was 61∼77years. In condition rating class, area of class 3 was 51,960$m^2$(32.8％), area of class 4 was 6,583$m^2$(3.5％), and area of class 5 was 4,086$m^2$(2.6％) and gross area of class 3∼6 need artificial restoration was 61,619$m^2$(38.9％). Considering actual vegetation, plant community structure, and condition rating class biotope was classified by total 14 types. While distribution area of Queens spp. old growth forest of shrub damaged(51,246$m^2$, 32.4％) and deciduous broad leaved old growth forest of simple-layer structure(19,906$m^2$, 12.6％) is large and that of deciduous broad-leaved old growth forest of multi-layer structure(2,085$m^2$, 1.3％) and Queens spp. old growth forest of multi-layer structure may have to manage with user control by administration plan for stabilization of Sangnim Woods ecosystem for long-term. Also, both vegetation of shrub damaged and simple-layer structure as negative restoration area should be restored for ecological succession and both grassland and planted area with korean woody plants as positive restoration area should be revegetated by using ecological planting model of native vegetation structure in Sangnim Woods.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.92-100
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• 2010

Combustion stability rating tests of 75-tonf-class thrust chamber for technology demonstration were carried out at a low pressure. Two kinds of mixing heads were used in this study. One of them has injectors of 631 and the other has injectors of 721. Mixing head with injectors of 631 showed a self-oscillation instability at the chamber pressure of 30 bar. Mixing head with injectors of 721 showed that a high frequency combustion stability was maintained under the same pressure and the same mass flow rate. But mixing head with injectors of 721 generated a self-oscillation instability at the chamber pressure of 20 bar and it was found that stability boundary region was changed due to the configuration of a mixing head from these results.

• Korean Journal of Environment and Ecology
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• v.29 no.4
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• pp.605-614
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• 2015

This study was carried out to maintain, manage and restore the trails by assessing the physical conditions, the patterns of deterioration and the impact rating class of the major trails of Juwangsan National Park. The major trails followed 4 routes including Jubong, Gamaebong, Janggunbong~Geumeungwangi and Woloe. The route length of Jubong was 4.6 km; it was 3.6 km for Gamaebong, 5.6 km for Janggunbong~Geumeungwangi and 5.9 km for Woloe. As for the physical conditions, Jubong was the widest and Janggunbong~Geumeungwangi was the narrowest in trail width. In terms of the bared trail width, Jubong was the widest and Janggunbong~Geumeungwangi was the narrowest. As for the depth of erosion, Gamaebong was the deepest and Woloe was the shallowest. Janggunbong~Geumeungwangi was the steepest and Gamaebong was the gentlest in the slope. Further, Gamaebong showed the highest soil hardness, and Woloe had the lowest hardness. In terms of the times of appearance of deterioration patterns, Jubong recorded 71 times, Gamaebong 62 times, Janggunbong~Geumeungwangi 63 times and Woloe 78 times. In case of the impact rating class, the trail erosion was similar to grades I and II grade; the rest were mostly I grade and hence considered to be in a generally good condition. For the ongoing management of trails, a comprehensive study needs to be conducted in the light of various environmental factors. Also, a restoration plan for damaged trails should be established with consideration for the surrounding environment and ecosystem.

• Journal of KIBIM
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• v.6 no.2
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• pp.29-38
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• 2016

Road bridges are deteriorating gradually, and it is forecasted that the number of road bridges aging over 30 years will increase by more than 3 times of the current number. To maintain road bridges in a safe condition, current safety conditions of the bridges must be estimated for repair or reinforcement. However, budget and professional manpower required to perform in-depth inspections of road bridges are limited. This study proposes an estimation model for safety rating of road bridges by analyzing the data from Facility Management System (FMS) and Yearbook of Road Bridges and Tunnel. These data include basic specifications, year of completion, traffic, safety rating, and others. The distribution of safety rating was imbalanced, indicating 91% of road bridges have safety ratings of A or B. To improve classification performance, five safety ratings were integrated into two classes of G (good, A and B) and P (poor ratings under C). This rearrangement was set because facilities with ratings under C are required to be repaired or reinforced to recover their original functionality. 70% of the original data were used as training data, while the other 30% were used for validation. Data of class P in the training data were oversampled by 3 times, and Repeated Incremental Pruning to Produce Error Reduction (RIPPER) algorithm was used to develop the estimation model. The results of estimation model showed overall accuracy of 84.8%, true positive rate of 67.3%, and 29 classification rule. Year of completion was identified as the most critical factor on affecting lower safety ratings of bridges.

• Korean Journal of Environment and Ecology
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• v.16 no.4
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• pp.465-474
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• 2003

According to rapid increase of visitors to the Baekdudaegan, the most important ecosystem in Korea, fur climbing or outdoor recreation, deterioration of natural environment along the trail on the ridge of Baekdudaegan is becoming more serious. The purpose of this study is to research the deterioration condition of the trail between Manbokdae and Bokseongijae on the Baekdudaegan with intent to prepare the conservational management strategy fur the trail on the ridge of Baekdudaegan. To accomplish the purpose, not only trail condition such as altitude, entire width, bare width, maximum depth and slope of trail, but also deterioration types of trail were surveyed at the total 232 points for 28.4km in length. Furthermore, impact rating class, which could be effective means to check the step and extent of deterioration process, was judged on each points of trail. Putting together these results informs us that the deterioration condition of the trail between Manbokdae and Bokseongijae is not reached the level of grave concern yet, but prompt countermeasure to maintain the existing condition has to be considered with regard for the conditions of location and the increasing amounts of use.

• Korean Journal of Environment and Ecology
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• v.18 no.2
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• pp.175-183
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• 2004

They are raising the necessity to prepare the conservational management strategy for the trail on the ridge of the Baekdudaegan where deterioration of natural environment along the trail as the rapid increase of visitors to the Baekdudaegan. The purpose of this study, followed after the Kwon and Lee(2003), is to research the deterioration condition of the trail between Namdeogyusan and Sosagogae on the Baekdudaegan. To accomplish the purpose, not only trail condition such as altitude, entire width, bare width, maximum depth and slope of trail, but also deterioration types of trail were surveyed at the total 182 points for 32.3km in length. Furthermore, impact rating class, which could be effective means to check the step and extent of deterioration process, was judged on each points of trail. Results informs us that the deterioration condition of the trail between Namdeogyusan and Sosagogae is not reached the level of grave concern yet, but some points and sections of trail are in urgent need of the integrated and organized maintenance. And some managerial strategies of trail were proposed in connection with the maintenance for trail on the Baekdudaegan ridge.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.29 no.3
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• pp.33-39
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• 2011

The purpose of this study is to present the raw data for establishing the conservation and restoration trail about Wolseong by objective and systematical trail deterioration in Wolseong as UNESCO, world heritage site, Gyeongju-si, Korea. To accomplish the purpose, not only trail condition such as altitude, entire width, bare width, maximum depth and slope of trail, but also deterioration types of trail were surveyed at the total 97 points for 2.145km in length on the 11 access trails to Wolseong. Major deterioration types of trail were root exposure(48%), rock exposure(40%), trail deeping(9%) in order of frequency. To grasp the deterioration condition of the trail, assessment on impact rating class of trail that the 11 access trail were investigated. Putting these results together informs us that the deterioration condition of the trail in Wolseong is reached the level of grave concern yet, prompt countermeasure to maintain the existing condition has to be considered with regard for the conditions of location and the containing amounts of use.

• Journal of Information Processing Systems
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• v.14 no.5
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• pp.1136-1149
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• 2018

With the increasing of urban electricity demand, making the most use of the power cable carrying capacity has become an important task in power grid system. Contrary to the rated ampacity obtained under extremely conservative conditions, this paper presents the various steady value of cable ampacity by using the changing surrounding parameters under operation, which is based on cable ampacity calculation equation under the IEC-60287 standard. To some degree, the cable ampacity analysis of actual surroundings improves the transmission capacity of cables. This paper reveals the factors that influence cable ampacity such as insulating layer thickness, allowable long-term conductor temperature, the ambient temperature, soil thermal resistance coefficient, and so on, then gives the class of the influence of these parameters on the ampacity, which plays a great role in accurately calculating the real-time ampacity and improving the utilization rate of cable in the complex external environment condition. Furthermore, the transient thermal rating of the cable is analyzed in this paper, and temperature variation of the conductor under different overload conditions is discussed, which provides effective information for the operation and control of the system.

• Korean Journal of Environment and Ecology
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• v.19 no.2
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• pp.130-138
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• 2005

The purpose of this study is to analyze the trail deterioration conditions and to obtain the informations for the desirable maintenance and restoration of the trails in Woraksan National Park. To accomplish the purpose, not only trail condition such as altitude, entire width, bare width, maximum depth and slope of trail, but also deterioration types of trail were surveyed at the total 111 points for 13.5km in length on the four access trails to Yeongbong which is the main peak of Woraksan. Furthermore, impact rating class, which could be effective means to check the step and extent of deterioration process, was judged on each points of trail. Results informs us that the deterioration condition of the trail in Woraksan National Park is not reached the lev- el of grave concern yet, but the active counterplan to change over from the safety-centric facility station to the integrated and organized restoration aiming to natural environment conservation is urgently needed.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.747-750
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• 2004

Lightweight concrete is known for its advantage of reducing the self-weight of the structures, reducing the areas of sectional members as well as making the construction convenient. Thus the construction cost can be saved when applied. to . structures such as long-span bridge and high rise buildings. However, the lightweight concrete requires specific design mix method that is quite different from the typical concrete, since using the typical mix method would give rise the material segregation as well as lower the strength by the reduced weight of the aggregate. In order to avoid such problems, it is recommended to apply the design mix method of high performance self-compacting concrete for the lightweight concrete. Therefore, this study introduces a production of self-compacting concrete, PF-modified and improved version of Nan-Su's design mix method of self-compacting concrete. Through a series of test mixes conducted during the study, the quality of the concrete at its fresh condition has been evaluated per the 2nd class rating standards of self-compacting concrete published by JSCE, especially focused in its fluidity, segregation resistance ability, and filling ability.