• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.2
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• pp.239-250
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• 2022

LoRa is a physical layer technology designed to secure highly reliable long-range communication with introducing loco parentis tree network and chirp spreading spectrum. Since since a leaf can send message to more than one parents simultaneously with a single transmission in a region, packet delivery ratio increases logarithmically as the number of gateways increases. The delivery ratio, however, dramatically collapses even under loco parentis tree topology due to the limitations of ALOHA-like primitive MAC, . The proposed method is intended to exploit SDMA approach to reuse frequency in an area. With the view, TxPower of each sender for each message in a concurrent transmission is elaborately controlled to survive the collision at different gateway. Thus, the gain from the capture effect improves the capacity of resource-hungry Low Power and Wide Area Networks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.194-198
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• 2021

LoRa is a physical layer technology that is designed to provide a reliable long-range communication with introducing CSS and with introducing a loco parentis tree network. Since a leaf can utilize multiple parents at the same time with a single transmission, PDR increases logarithmically as the number of gateways increases. Because of the ALOHA-like MAC of LoRa, however, the PDR degrades even under the loco parentis tree topology similarly to the single-gateway environment. Our proposed method is aimed to achieve SDMA approach to reuse the same frequency in different areas. For that purpose, it elaborately controls each TxPower of the senders for each message in concurrent transmission to survive the collision at each different gateway. The gain from this so-called capture effect increases the capacity of resource-hungry LPWAN. Compared to a typical collision-free controlled-access scheme, our method outperforms by 10-35% from the perspective of the total count of the consumed time slots. Also, due to the power control mechanism in our method, the energy consumption reduced by 20-40%.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.2
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• pp.86-93
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• 2007

We analyzed the aquatic insects and stomach contents of chum salmon (Oncorhynchus keta) fingerings which were collected at Namdae stream in Yangyang. A total of 6 orders, 25 family, and 52 species of aquatic insects have been found in the study area. The majority of prey eaten by chum salmon fingerlings was Diptera, which occupied 91.7% of prey items by number and 40.9% by wet weight. The food items from juvenile salmon stomachs were matched with living organisms in the river. Therefore it seemed that there was no food selectivity of juvenile chum salmon in Namdae stream. The stomach contents of masu salmon fry showed a similar pattern to the fingerlings of chum salmon. This result will provide information on the carrying capacity of Namdae stream for chum salmon.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.3
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• pp.138-147
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• 2007

An emergy concept was used to evaluate the environment and economy of the Han River basin in Korea and to suggest policy perspectives far the sustainable utilization of its environment and associated estuarine ecosystem. The economy of the basin used $5.19{\times}10^{23}\;sej/yr$ of emergy in 2005. The economy of the Han River basin was heavily dependent on outside energy sources from foreign countries and other parts of Korea, with internal sources, renewable and nonrenewable, contributing only 15.6% to the total emergy use. The basin's trade balance in terms of emergy showed trade surplus, whereas there was a deficit in monetary terms. The population of the Han River basin was far greater than the carrying capacity calculated using the emergy flow, with renewable carrying capacity only at 1.8% of the basin's population and developed carrying capacity at 14.3%. The economy of the basin imposed a substantial stress on its environment, with an environmental loading ratio of 54.8. Overall, the economy of the Han River basin was not sustainable with an emergy sustainability of 0.02. These are reflected in lower quality of living expressed in the emergy term than the national average. Deconcentration of population and economic activities is needed to reduce environmental stress on the environment of the basin and its valuable estuarine ecosystem. Policies to restore ecosystem productivity of the basin are also needed to ensure the sustainability of the basin's economic activities and the sustainable utilization of the Han River estuary. In this regard, it is urgently needed for the Korean government to implement sustainable management measures for the Han River estuary, a well-preserved, productive natural estuarine ecosystem in Korea.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.2
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• pp.135-143
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• 2008

An emergy concept was used to evaluate the environment and economy of the estuarine areas of Yeongsan River, Seomjin River, and Han River in Korea. The emergy evaluations clearly showed ecological and socioeconomic characteristics of the estuarine areas that act as ecological and economic centers of surrounding areas. River, tide, and rain provided most of the renewable emergy inputs to the estuarine areas with their contribution to the total emergy input less than 8%. The estuarine areas mostly relied for their operation on the purchased emergy which accounted for $92{\sim}98%$ of the total emergy input to the systems. Emergy indices such as emergy use per unit area, population carrying capacity, environmental loading ratio, and emergy sustainability index revealed that the estuarine areas of Yeongsan River, Seomjin River, and Han River are not sustainable at the current level of economic activities in the areas. The ecological economic values of the environment of the areas were in the range of $7.29{\sim}22.06$ million Em\/ha/yr. They are more than twice that for the whole country, indicating the ecological and economic importance of the eatuarine areas. It is, therefore, urgent to establish and implement estuarine management policies to protect and restore the ecological and economic potentials of the estuarine areas of Yeongsan River, Seomjin River, and Han River. Management plans for the estuarine areas should include both demand-side measures such as reduction of population and economic concentration and consideration of ecological carrying capacity in planning stages for utilization and development of the areas, and supply-side ones such as restoration of degraded ecosystems and construction of new productive ecosystems.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.2
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• pp.92-106
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• 1996

Imaginary grass field was assumed suitable as the representative one for simplified estimation of local drought, and a moisture balance booking model computing drought was developed with the limited numbers of its determining factors, such as crop coefficient of the field, reservoir capacity of the soil, and the beginning point of drought as defined by soil moisture status. The maximum effective rainfall was assumed to be the same as the available free space of soil reservoir capacity. The model is similar to a definite depth evaporation pan, which stores rainfall as much as the available free space on the water in it and consumes the water by evaporation. When the pan keeps water less than a certain defined level, it is droughty. The model simulates soil moisture deficit on the assumed grass field for the drought estimation. The model can assess the water requirement, drought intensity, and the index of yield decrement due to drought. The influencing intensity indices of the selected factors were 100, 21, and 16 respectively for crop coefficient, reservoir capacity, and drought beginning point, determined by the annual water requirements as influenced by them in the model. The optimum values of the selected factors for the model were respectively 58% for crop coefficient defined on the energy indicator scale of the small copper pan evaporation, 50 mm for reservoir capacity on the basis of the average of experimentally determined values for sandy loam, loam, clay loam, and clay soils, and 65% of the reservoir capacity for the beginning point of drought.

• Journal of Plant Biology
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• v.36 no.4
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• pp.363-370
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• 1993

Experiments with non-nodulated alfalfa (Medicago sativa L. cv, Europe) plants grown in hydroponic cuiture, were carried out to estimate the remobiJization of nitrogen (N) reserves and to investigate the transported forms of reduced soluble-N in xylem during regrowth following shoot removal. Endogenous N remobilization were estimated by $^{15}N$ labelling and amino acids in xylem sap were analysed. The, $^{15}N$ contents of ~egr9wing leaves and stems increased as a result of remobilization of N reserves mainly from root ,system, Regrowing leaves were a stronger sink than regrowing stems, with about tWo-thirds of remobilized 15N being recoved in leaves. Endogenous N in lateral roots accounted for about 46% of the total N reserves used for regrowth, while tap roots accounted for 23%, About 72% of total endogenous N remobilized to regrowing shoot, occurred during the first 10 days of regrowth, The outflow of reduced soluble-N (mainly amino acids) was greater than that of protein-N, while the latter was the largest storage pool in tap root and lateral roots. It is suggested that amino acids-N was the most readily avaiable form of N reserves. Asparagine, which repre5ented about 75% of amino acids-N in xylem sap, was the main transported form of reduced N. Its relative contents, during the first 10 days of regrowth, decreased from 75% to 59%. This decline was accompanied by compensatory increase in the relative contents of asparatate and glutamine.

• Korean Business Review
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• v.21 no.2
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• pp.57-77
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• 2008

Mountain destination plays a vital role in satisfying the demand of natural tourism products, provides exclusive leisure, adventure and unique cultural experience. The Himalayan region includes some of the most biologically diverse habitats on Earth as well as homes to a bewildering variety of culture. The purpose of this study is to figure out the mountain tourism as a tool of sustainable development and explore the tourism destination development strategies with case study of Himalayan area. In this study, we recognized the importance of tourism for the isolated developing communities, for which, tourism provide the way of developing its economic and society. It also generates new opportunities of employment and change the soclo-economic environment of region. The hilly terrain of the state lacks reliable transportation infrastructure, therefore tourism is the only industries to support the economy and to uplift the standard of living for the people of Himalayan region. The region has large potential in the natural and cultural based tourism. The tourism development of the state may have cultural and ecological impact in future. Therefore, the planning and successfully promoting long-term policy and developing more sustainable tourism is important.

• Korean Journal of Environmental Biology
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• v.29 no.4
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• pp.280-285
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• 2011

As the plants grow in a fixed place, they can be a good indicator which reflects the level of environmental pollution. It is necessary for them to develop a strategy to cope with stress under unfavorable environmental conditions. In this study, spindle trees ($Euonymus$ $japonica$) were collected from a clean area (Kijang) as well as a heavily polluted area (Onsan) to check applicability of irradiation combined with plant bioassay to environmental monitoring. The leaves were irradiated with 0, 50 and 100 Gy of gamma rays, and then evaluated for antioxidative capacity with 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and superoxide dismutase (SOD) analysis. The result shows that there was no significant changes in SOD and EDA (Electron Donationg Ability) in the samples collected from a polluted area. In the meanwhile, SOD increased in the samples from a clean area until 6 to 10 hours after irradiation, then it decreased gradually until 24 hours after irradiation. In conclusion, the plants in the polluted area have developed higher resistance to oxidative stress induced by ionizing radiation than those in the relatively clean area. Irradiation combined with plant bioassay on enzymatic activities and free radical scavenging capacity has proven to be a possible tool for biomonitoring the environmental pollution.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.423-429
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• 2001

Prediction of the variation in annual biomass was conducted for the white croaker. Argyrosomus argentatus in Korean waters using leslie Matrix, based upon fishery data for the past 21 years and biological data, We used density-independent and density-dependent Leslie Matrix models. Similar parameters were estimated from two models except that the density-dependent model was influenced by the density effect variable, q(i,t), The eigenvalue of the white croaker population for the $1984\~1995$ period was estimated to be 0.8, indicating a declining pattern of the population. The survival rate of 0-th year class was calculated to be 0.00005. Based on the schedule of the age-specific survival rate and fecundity, the future biomass and catch was predicted for various levels of fishing mortalities (F), If F was set at 0.252/yr ($F_{35x}$) or 0.368/yr ($F_{0.1}$), the biomass and catch increased, and if F was set at 0.922 ($F_{current}$), the biomass and catch decreased, The fishing mortality at equilibrium was estimated to be 0.7/yr. Finally, the management strategy of the white croaker was discussed.