• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.115-123
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• 2009

Grazing effects of a freshwater bivalve, Unio douglasiae, on both the phytoplankton communities of cold- and warm eutrophic lakes were examined in aquarium with sediment. The animal U. douglasiae used in the study was collected from the Gunsan (Jeonbuk), acclimatized in laboratory aquaria with washed sand from the mussel collection stream, and starved for $2{\sim}3$ days by the experiment. Grazing experiments were performed with the surface waters collected from Lake Ilgam (Seoul) in the cold period (March 31, 2008), and the warm period (June 19, 2008), respectively. Results clearly showed that the concentration of chlorophyll-a (chl-a) and algal abundance were decreased with the increase of mussel-treated density and treated-time. At the same animal density, U. douglasiae effectively decreased the chl-a of cold-lake water (CW), compared to warm-lake water (WW). Increasing the mussel density, the filtering rate (or algal abundance) of the mussel on the CW gradually decreased, while those of WW did not increase or decrease. Major phytoplankton species Synedra ulna and Stephanodiscus hantzschii, and Scenedesmus ecornis in CW, and those of Tetraedron regulare and Pediastrum simplex in WW, were quickly decreased after the mussel stocking. Interestingly, cyanobacterium Microcystis aeruginosa in WW, not dominant species, were less removed. These results suggest that a freshwater bivalve U. douglasiae have a strategic potential to control dense hibernal diatom or green algae, rather than the cyanobacterial bloom in eutrophic water.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.6A
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• pp.63-73
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• 2008

RFID(Radio Frequency IDentification) system is an automated identification system that basically consists of tags and readers and Back-End-Databases. Tags and Readers communicate with each other by RF signal. As a reader can identify many tags in contactless manner using RF signal, RFID system is expected to do a new technology to replace a bar-code system in supply-chain management and payment system and access control and medical record and so on. However, RFID system creates new threats to the security of systems and privacy of individuals, Because tags and readers communicate with each other in insecure channel using RF signal. So many people are trying to study various manners to solve these problems against attacks, But they are difficult to apply to RFID system based on EPCglobal UHF Class-1 Generation-2 tags. Recently, Chien and Chen proposed a mutual Authentication protocol for RFID conforming to EPCglobal UHF Class-1 Generation-2 tags. we discover vulnerabilities of security and inefficiency about their protocol. Therefore, We analyze vulnerabilities of their protocol and propose an efficient mutual authentication protocol that improves security and efficiency.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.59-67
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• 1983

An experiment on the rearing of tilapia stocked in closed recirculating tanks eliminating biological filter beds was carried out at the Fish Culture Experiment Station of the National Fisheries University of Pusan, from May 18 through October 21, 1982, and the growth rates, feed conversion, water quality, spawning prevention and space utilization efficiency were discussed. Finally discussed is the feasibility on the establishment of commercial production units. On the water quality, the water temperature ranged from $22.8^{\circ}C\;to\;29.1^{\circ}C$, and total ammonia arround 10 ppm or slightly up. Maintaining phytoplankton bloom was not successful probably because of the active consumption by the heavily stocked tilapia. Several attempts were made by changing the culture water with green water from a nearby earthen pond with results of fading-away in a couple of days. Feed conversions were relatively high ranging from 0.9 to 1.2 except for experiment 1 when the fish were not fully recovered from weakened wintering state. The feed used was partly laboratory prepared $25\%$ protein diet and mostly commercially available $39\%$ protein carp feed. Spawning was completely controlled during the experiment, resulting from density effect, which ranged from 10kg to 40.7kg per square meter with water depth of 0.5 to 0.6m. Space utilization efficiency was very high. Daily net production from the experiment division 3, which showed the highest result, was 6.206 kg per tank, which is calculated 3,235 metric tons per hectare per year, This time, water temperature ranged from 27.8 to $29.1^{circ}C$, average being $28.4^{circ}C$, and total ammonia arround 10 ppm. An estimation for the commercial set-up of the production system based on the results of experiment divisions which had initial stocking rate $15\;kg/m^2$ or up, is made. If the total facility, 8 tanks comprising $56\;m^2$ in surface area, is used for the present study, the yield would become 5,639 kg from 200 day rearing, which would be possible under double sheets vinyl house without additional heating, and it is thought feasible in the economic view point, when 10 or more units are operated.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.221-230
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• 2016

Multi-functional floating wetland island (mFWI) was developed in order to prevent algal bloom and to improve water quality through several unit purification processes. A test bed was applied in the stagnant watershed in an urban area, from the summer to the winter season. For the advanced treatment, an artificial phosphorus adsorption/filtration medium was applied with micro-bubble generation, as well as water plants for nutrient removal. It appeared that the efficiency of chemical oxygen demand (COD) and total phosphorus (T-P) removal was higher in the warmer season (40.9%, 45.7%) than in the winter (15.9%, 20.0%), and the removal performance (suspended solid, chlorophyll a) in each process differs according to seasonal variation; micro-bubble performed better (33.1%, 39.2%) in the summer, and the P adsorption/filtration and water plants performed better (76.5%, 59.5%) in the winter season. From the results, it was understood that the mFWI performance was dependent upon the pollutant loads in different seasons and unit processes, and thus it requires continuous monitoring under various conditions to evaluate the functions. In addition, micro-bubbles helped prevent the formation of anaerobic zones in the lower part of the floating wetland. This resulted in the water circulation to form a new healthy aquatic ecosystem in the surrounding environment, which confirmed the positive influence of mFWI.