• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.368-372
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• 2004

The development of a benthic filamentous green algal community formed by Spiro gyra sp. in early summer has been observed in the littoral zones in the north basin of Lake Biwa since the 1980s. The development of a Spirogyra sp. community may have an effect on the increase in the biomass of the benthic algal community in early summer and on the alterations in seasonal fluctuation patterns of the biomass. In this mini-review, the causes underlying the development of the Spirogyra sp. community are discussed on the basis of studies in the seasonal fluctuations of benthic algal communities in littoral stony zones carried out in 1963-1964, 1995-1996 and 2000-2001, especially those focusing on the nutrient concentration $(NO_3^--N)$. $NO_3^--N$ concentrations in June were higher than $100{\mu}g\;L^{-1}$ in 1995 and 2000 in contrast to a concentration in June 1964 of only $20{\mu}g\;L^{-1}$. These results show that $NO_3^--N$concentrations throughout in 1963-1964 period were considerably lower than those in 1995-1996 and 2000-2001, suggesting that the $NO_3^--N$concentration may have served as a limiting factor on Spirogyra sp. growth in 1963. $NO_3^--N$ concentrations in the pelagic zone in the north basin of Lake Biwa have clearly increased from the 1950s under the impact of economic growth and the increasing population in the watershed. The development of the Spirogyra sp. community seems to be the result of a heady increase in the nutrient supply from human activities.

• Korean Journal of Ecology and Environment
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• v.47 no.4
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• pp.328-336
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• 2014

Nakdan weir, which is located in the second weir among the 8 weirs of Nakdong River, had been constructed from Nov. 2009 to Nov. 2011. To analyze the effect of Nakdan weir construction on benthic macroinvertebrates, we studied 2 sites around Nakdan weir (upstream and downstream) from 2007 to 2014. The average numbers of species and individuals were decreased after the construction (in 2012~2014, 51 species $895inds.\;m^{-2}$) than before construction (in 2007~2009, 25 species $84inds.\;m^{-2}$), especially in upstream site of Nakdan weir. After the construction, especially in 2012, dominance indices (DI) were increased by the decline of some specific taxon population, such as Ephemeroptera and Trichoptera, etc. After construction, individual ratios of GC (Gathering Collectors) and P (Predator) of FFGs (Functional feeding groups) and BU (Burrowers) of HOGs (Habitat orientation groups) were higher than before construction. So the results of this study indicate that the changes by a weir construction, such as the decline of shallow depth area, reduced velocity of water flow and increased ratio of sand bed, etc., can affect the benthic macroinvertebrate communities variously.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.295-302
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• 2016

Underwater acoustic communication channel is often defined as a multipath fading channel since the multipath arrivals from various paths interfere with each other and cause frequency dependent constructive or destructive interference in received signals. Therefore signal-to-noise ratio (SNR) of received signal fluctuates as a function of frequency. In addition, sea surface fluctuation induces frequency dependent time variant signal fading due to coherent component variation of surface bounce path. The frequency shift keying (FSK) system is known to be less sensitive and more robust under these interference and fading, and M-ary frequency shift keying (MFSK) system is adopted to increase a data rate. In this study, a bit error rate (BER) of 4 channels 4FSK system are examined in shallow sea multipath channel. Experimental results show that RS code reduces efficiently the BER of 4FSK system since frequency dependent time-varying fading is characterized to give burst errors. The BER of a different data rate or different source-to-receiver range depends on not only the channel coherent bandwidth but also frequency dependent multipath fading.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.69-79
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• 2017

Protected area of water for supply source is located mostly of rural area in Korea. Normally, sewage treatment system is poor to manage in rural, because low population and density. Rural area need sewage treatment system to supervise supply source of water. In this study, analysis on operation result of 4 RCSTP and MWTP is located at the rural area. Higher concentration of pollutant were inflows to MWTP than RCSTP, and effluent quality standard is satisfaction. However, RCSTP effluent pollutant concentrations was researched higher than MWTP. The organic matter(BOD, COD) were about 5% of a high treatment efficiency to a median. The nutrient(T-N, T-P) were detected Up to high 30%. Also, we analyzed to effect reactor operational parameters on the pollutant treatment efficiency like mixed liquer suspended solid(MLSS), dissolved oxygen(DO) and sludge retention time(SRT). As a result, pollutant treatment efficiency showed fluctuation in accordance with operating condition. Thus, it is necessary to manage the reactor operation condition for management of rural area sewage treatment.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.256-260
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• 2006

This study was conducted to investigate the effect of parasititoids on the density-fluctuation of the pine needle gall midge, Thecodiplosis japonensis. The density of T. japonensis and its parasitoids was observed by emergence trap in pine forest in Namsung-dong, Keumho-eup, Youngcheon-shi, Kyeongsangbuk-do, Korea, from 1986 to 2005. After 1987, density fluctuations of adults pine needle gall midge and its parasitoids showed similar trends and density of parasitoids was dependent on density of host population. Sex ratio of the pine needle gall midge, T. japonensis, was female-biased and had some variations in according to years. These trends were similar to those of parasitoid populations and sex ratio of Inostemma seoulis was more female-biased than that of I. matsutama. T. japonensis adults emerged in the field from May 16 to July 27 and the peak of emergence was between late May and early June. The adults of Inostemma matsutama emerged from May 16 to June 11 (peak between late May and early June), whereas those of Inostemma seoulis emerged from June 9 to July 27 (peak: late June).

• Korean Journal of Environmental Biology
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• v.34 no.1
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• pp.56-62
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• 2016

Pest population density models are very important to monitor the initial occurrence and to understand the continuous fluctuation pattern of pest in pest management. This is one of the major issues in agriculture because these predictions make pesticides more effective and environmental impact of pesticides less. In this study, we combined and predicted the mortality change of pest caused by pesticides with temperature change and population dynamic model. Sensitive strain of two-spotted spider mite (Tetranychus urticae Koch) with kidney bean leaf as host was exposed to mixed acaricide, Acrinathrin-Spiromesifen and organotin acaricide, Azocyclotin, at 20, 25, 30, and $35^{\circ}C$, respectively. There was significant difference in mortality of T. urticae among pesticides and temperatures. We used DYMEX to simulate population density of T. urticae and predicted that the initial management time and number of chemical control would be changed in the future with climate change. There would be implications for strategies for pest management and selection process of pesticide in the future corresponding climate change.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.217-224
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• 2005

This study was aimed to analyze the long-term fluctuation of water quality and phytoplankton dynamics of Paldang reservoir in Korea and to assess the relationship between algal bloom patterns and hydrological, limnological data. Diatoms in Paldang reservoir occurred continuously through the year. Blue- green algae occurred during the summer season (from June to Sept.), and the highest count was observed in July. Occurrence pattern of green algae was similar to that of blue-green algae. The rest of algae contained a lot of Cryptomonas spp. whose concentration was high from May to Aug. Dominant algal genera (>>7,000 cells $mL^{-1}$) in Paldang reservoir were Aulacoseira, Cyclotella, Microcystis, and Cryptomonas spp. Microcystis and Anabaena occurred during the summer season. Many different green algal genera were found in Paldang reservoir but their abundances were very low. There were some significant correlations (r>0.3, p<0.05) between algal taxa and water quality; diatoms and water temperature, TP:blue-green algae and water temperature, pH, DO saturation, COD, TP; green algae and water temperature, pH, DO saturation, COD, SS, TP. Furthermore, algal genera and water quality was significantly correlated (r>0.3, p<0.05) ; Aulacoseira and TN, TP; Anabaena and water temperature, DO saturation, COD, TP : Microcystisand water temperature, pH, DO saturation, TP; Coelastrum and COD, SS; Scenedesmus and water temperature, COD, TN, TP; Cryptomonas and DO saturation, TN. In Paldang reservoir, the water temperature had relatively big effect on blue-green algal bloom that was also dependant upon its hydrologic condition.

• Applied Chemistry for Engineering
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• v.19 no.2
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• pp.228-235
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• 2008

Nickel plating thickness increased with the electric current density, and the augmentation was more thick in $6{\sim}10A/dm^2$ than low current. Hull-cell analysis was tested to evaluate the current density. Optimum thickness was obtained at a temperature of $60^{\circ}C$, and the pH fluctuation of 3.5~4.0. Over the Nickel ion concentration of 300 g/L, plating thickness increased with the current density. The rate of decrease in nickel ion concentration was increased with the current density. The quantity of plating electro-deposition was increased at the anode surface, which was correlated with the increase of plating thickness. The plating thickness was increased because of the quick plating speed. However, the condition of the plating surface becomes irregular and the minuteness of nickel plating layer was reduced with the plating rate. After the corrosion test of 25 h, it was resulted in that maintaining low electric current density is desirable for the excellent corrosion resistance in lustered nickel plating. According to the program simulation, the thickness of diffusion layer was increased and the concentration of anode surface was lowered for the higher current densities. The concentration profile showed the regular distribution at low electric current density. The field plating process was controlled by the electric current density and the plating thickness instead of plating time for the productivity. The surface physical property of plating structure or corrosion resistance was excellent in the case of low electric current density.

• Journal of Internet Computing and Services
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• v.19 no.3
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• pp.49-56
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• 2018

Euclidean distance (ED) between error distribution and Dirac delta function has been used as an efficient performance criterion in impulsive noise environmentsdue to the outlier-cutting effect of Gaussian kernel for error signal. The gradient of ED for its minimization has two components; $A_k$ for kernel function of error pairs and the other $B_k$ for kernel function of errors. In this paper, it is analyzed that the first component is to govern gathering close together error samples, and the other one $B_k$ is to conduct error-sample concentration on zero. Based upon this analysis, it is proposed to normalize $A_k$ and $B_k$ with power of inputs which are modified by kernelled error pairs or errors for the purpose of reinforcing their roles of narrowing error-gap and drawing error samples to zero. Through comparison of fluctuation of steady state MSE and value of minimum MSE in the results of simulation of multipath equalization under impulsive noise, their roles and efficiency of the proposed normalization method are verified.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.2
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• pp.96-104
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• 2001

Usage of ecosystem models has been extended to landscape scales for understanding the effects of environmental factors on natural and agro-ecosystems and for serving as their management decision tools. Accurate prediction of spatial variation in daily temperature is required for most ecosystem models to be applied to landscape scales. There are relatively few empirical evaluations of landscape-scale temperature prediction techniques in mountainous terrain such as Korean Peninsula. We derived a periodic function of seasonal lapse rate fluctuation from analysis of elevation effects on daily temperatures. Observed daily maximum and minimum temperature data at 63 standard stations in 1999 were regressed to the latitude, longitude, distance from the nearest coastline and altitude of the stations, and the optimum models with $r^2$ of 0.65 and above were selected. Partial regression coefficients for the altitude variable were plotted against day of year, and a numerical formula was determined for simulating the seasonal trend of daily lapse rate, i.e., partial regression coefficients. The formula in conjunction with an inverse distance weighted interpolation scheme was applied to predict daily temperatures at 267 sites, where observation data are available, on randomly selected dates for winter, spring and summer in 2000. The estimation errors were smaller and more consistent than the inverse distance weighting plus mean annual lapse rate scheme. We conclude that this method is simple and accurate enough to be used as an operational temperature interpolation scheme at landscape scale in Korea and should be applicable to elsewhere.