• Korean Journal of Veterinary Service
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• v.21 no.4
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• pp.431-437
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• 1998

Argulus spp, a small group of parasitic curstaceans called Branchiura, is particularly important in freshwater acquaculture. We investigated the infection of Argulus to several different species of fishes and therapy effect of masoten. Argulus japonicus was collected from Okjeong lake, Chonbuk province and experlmen-tally infected to freshwater fishes from July to August 1998. The results were as follows ; 1. The shape of a Agulus is an oval and dorsoventrally flattened, with first maxillae and second maxillae, and four pairs of legs. 2. The size of the adult stage of A japonicus was 3.2-5.0$\times$2.3-2.9mm in female and 1.5-3.1$\times$1.6-2.9mm in male. 3. In the trial of experimental infection with A japonicus to non-scaled fishes, Parasilurus asotus and Ictalurus punctalus, were infected and some of them died after severe infection. However, A japonica was not infected at all. 4. Masoten treatment for A japonicus was effective at 0.2 ppm once a day for 3 days and parasites on the surface of fishes disappeared after five days.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.413-419
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• 2014

Underwater acoustic channel has time-variability. Time varying channel which disturbs the continuous transmission of information data reduces the underwater acoustic communication performance. In this paper, we show the temporal coherence as time-variability of channel and indicate throughput efficiency in accordance with transmission time of information data. Then we analyzed influence of underwater channel time-variability on communication throughput efficiency. We confirmed that the throughput efficiency reduced when the time-variability of the channel increased via lake trial.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.1
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• pp.74-86
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• 2014

The optimization techniques are explored in the direction of arrival (DOA) estimation based on single acoustic pressure gradient vector sensor (APGVS). By analyzing the working principle and measurement errors of the APGVS, acoustic intensity approaches (AI) and the minimum variance distortionless response beamforming approach based on single APGVS (VMVDR) are deduced. The radius to wavelength ratio of the APGVS must be not bigger than 0.1 in the actual application, otherwise its DOA estimation performance will degrade significantly. To improve the robustness and estimation performance of the DOA estimation approaches based on single APGVS, two modified processing approaches based on single APGVS are presented. Simulation and lake trial results indicate that the performance of the modified approaches based on single APGVS are better than AI and VMVDR approaches based on single APGVS when the radius to wavelength ratio is not bigger than 0.1, and the two modified DOA estimation methods have excellent estimation performance when the radius to wavelength ratio is bigger than 0.1.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.327-334
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• 2010

The paper describes the history and the evolution of the conflict of the Saemangeum reclamation project, focusing on the court trial processes. The Saemangeum project is the world largest coastal reclamation work, regarded as the most controversial environmental issue in the recent history of Korea. Due to the severe pollution found in Lake Sihwa in 1996, the Saemangeum project began to receive a large degree of public concern on the water quality of the proposed artificial freshwater lake. Unlike the Sihwa case, the Korean court system intervened to resolve the heated conflicts between stakeholders in the Saemangeum case. Based on the same set of facts, the Korean courts showed different perspectives on the economic feasibility, value of the ecosystem, land use, and water quality, which represents the limit of legal system to address complicated environmental problems. After the final judgment by the Supreme Court, 'the Special Act for the promotion of the Saemangeum reclamation project', was enacted with strong political support from local leaders and congressmen. A more developmental-oriented land use plan came out in 2009 based on this Act. The Saemangeum project walked along the different pathway from the Sihwa case. The area should be managed in sustainable manners to appropriately consider conservation and development for the prosperity of local residents and future generations.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.368-374
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• 2016

This paper presents constructing transmitter and receiver by using a direct sequence spread spectrum techniques to DPSK (Differential Phase-Shift Keying) scheme in underwater acoustic communication. Since DPSK signal can be demodulated if the receiver knows only the phase difference between the adjacent bits, DPSK receiver structure has the advantage of being simplified. In the conventional receiver, two adjacent symbols of transmitted signal before despread are passed to the transition correlator that detects data by comparing maximum correlation outputs. At this time, the error for maximum value of the correlator output may increase because of low SNR (Signal to Noise Ratio) or high Doppler shift frequency according to the underwater channel. In this paper, we propose a method for accurate detection result using the width as well as the magnitude among outputs produced by the correlator. The performances of the proposed method was evaluated by simulation and lake trial data.