Gwan-Gyu Lee

Design of hybrid authentication scheme and key distribution for mobile multi-hop relay in IEEE 802.16j

Mobile multi-hop relay (MMR) network is known to have the strength of easy installation and convenient management because of its self-organizing and self-healing characteristics. However, MMR is also known to be vulnerable to security problems for the very same reason. In this paper, we propose a new hybrid authentication algorithm for IEEE 802.16j MMR network service. The proposed scheme uses centralized authentication when a mobile station (MS) or a relay station (RS) initially joins the MMR network, and uses distributed authentication for hop-by-hop authentication between the mobile nodes. We analyze the procedure of the proposed scheme in detail, and examine its usefulness when applied to the MMR network. The proposed scheme can be used in any mobile multi-hop network as well as IEEE 802.16j MMR network.

Calculating total urban forest volume considering the carbon cycle in an urban area – focusing on the city of Chuncheon in South Korea.

With the recent threat of climate change, the issue of carbon emission mitigation has become one of the fastest growing international agendas. The major cause of pan-international climate change is the increase of CO2 intensity in the atmosphere. It is possible, nonetheless, to sustain the carbon cycle when green plants, the only organic sink, exist in proper quantity. The main purpose of this current study is to quantitatively analyze the urban forest volume required to absorb carbon from a densely populated area. The study calculates CO2 emissions and uptake by urban forest volume in a given area, as well as the total urban forest volume required to absorb all of the emitted CO2. In a survey in the city of Chuncheon, the volume of CO2 emissions and that of the CO2 that can be absorbed was 2,211,586.74 and 30,455.48 tons, respectively, which means that approximately 2,181,129.26 additional tons need to be absorbed by urban forest volume. By the second-grade vegetation standard, it is necessary to secure 101,921.93 ha of coniferous forest, 103,371.06 ha of broad-leaved forest, or 103,863.30 ha of mixed forest. The urban area within the city of Chuncheon covers only 5303.04 ha, which clearly implies that urban forest alone cannot absorb the CO2 emissions in the area. Therefore, it follows that additional mitigation efforts need to be taken along with securing as much urban forest as possible.

Value Assessment for Inland Wetlands according to Ecological Geographic Distribution

Korea established an inventory of 1,916 sites of inland wetlands during a nationwide investigation from 2000 to 2010. If inland wetlands is included in or near various protected areas designated by the government, it can be selected as a wetland to be managed with priority. This study evaluated the aspect of management of inland wetlands by analyzing the correlation between locations of national protected areas and inland wetlands. As a result, it was shown that a considerable percentage of current inland wetland was located in areas that were designated and managed as protected areas by the government, as they had a high value of natural environment protection (527 sites, 31.61 %). When the range was widened to a radius of 1 km for protected areas, 959 sites were included and 57.53 % of sites were located in or nearby the protected areas. Among them, 46.79 % of sites were distributed up to or within a 1 km radius of waterside areas and rivers; it accounted for 81.33 % of wetlands located in protected areas. Therefore, it was found that locations of current inland wetlands were mostly in contact with rivers. The results of overlay analysis were classified into high, medium and low; the correlation of location with inland wetlands was analyzed through the analysis of separation distance of various protected areas. The number of wetlands located in areas of a ‘high’ value of protection was 998 (59.87 %); 289 sites (17.34 %) were distributed in areas of a ‘low’ value of protection. This implies that these wetlands are located in artificial areas and are more exposed to environmental pressures. Thus, these wetlands could be determined as inland wetlands, which we considered for the establishment of measures to prevent damage.

Zoning classes for forest visual landscape management in and around Pyeongchang Winter Olympic area: focused on Alpensia district in the city of Pyeongchang, Gangwon-do

Korea is preparing to host the 2018 Winter Olympics in Pyeongchang. The region surrounding Pyeongchang mostly consists of forested areas. To manage this region, it is necessary to design a process designating different management areas such as those allowing the formation of artificial and concentrated landscapes and restricted areas for conservation of the landscape. This study identifies methods for analyzing the degree of forest landscape management and level of visual sensitivity and subdivides the visible areas surrounding the region where the Winter Olympics will be held into different classes. As a result, four different classes were subdivided and the areas were divided into conservation zones, buffer zone 1, buffer zone 2, and transitional zones. The areas in the fourth class (transitional zone), where artificial and aggressive forest landscape management is possible, were primarily subjected to frequent movement and high levels of use. These areas included roads, city streets, areas surrounding the stadiums, accommodation facilities, and the observatory. It will be necessary at a later date to conduct an itemized and more detailed analysis regarding forest landscape design to create landscapes that correspond to the characteristics of the region in each subdivision.

Effects of Water Level Change on Wetland Vegetation in the Area of Riparian Forest for Dam Construction Period -Focused on the Hantan River Dam-

This study was performed to monitor the effects of water level change on changes of landscape, vegetation community, and species diversity of riparian forest. Hantan river dam, study area, has been constructed in the area of Chansoo-myeon, Pocheon-si and Yeoncheon-eup, Yeoncheon-gun, Gyeonggi-do, which is a dam for flood control only in flooding season. Landscape changes were notable after the construction of coffer dam, and the changes were caused by water level increase in areas of riparian forests which consisted of mainly withered willow as a dominant species in the flooding season. It changed vegetation communities of riparian forest from Phragmites japonica and Salix koreensis to Phragmites japonica. Species diversity index was lowest in 2010 when the coffer dam was constructed and showed an increasing trend later. Thus, this study is well in agreement with a previous report that plants of the genus Salix wither by muddy water during flooding and also suggests, controlling water level of river and prediction of water level changes effects should be considered when any facilities are planned.