• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.17-23
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• 2024

Losses in domestic water supply due to leaks are very large, such as fractures and defects in pipelines. Therefore, preventive measures to prevent water leakage are necessary. We propose the development of a leakage detection sensor utilizing vibration sensors and present an optimal leakage detection algorithm leveraging artificial intelligence. Vibrational sound data acquired from water pipelines undergo a preprocessing stage using FFT (Fast Fourier Transform), followed by leakage classification using an optimized tree-based boosting algorithm. Applying this method to approximately 260,000 experimental data points from various real-world scenarios resulted in a 97% accuracy, a 4% improvement over existing SVM(Support Vector Machine) methods. The processing speed also increased approximately 80 times, confirming its suitability for edge device applications.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.815-821
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• 2009

Information processing in variable and noisy environments is usually accomplished by means of adaptive filters. Among various adaptive algorithms, Least Mean Square (LMS) has become the most popular for its robustness, good tracking capabilities and simplicity, both in terms of computational load and easiness of implementation. In practical application of the LMS algorithm, the most important key parameter is the Step Size. As is well known, if the Step Size is large, the convergence rate of the algorithm will be rapid, but the steady state mean square error (MSE) will increase. On the other hand, if the Step Size is small, the steady state MSE will be small, but the convergence rate will be slow. Many researches have been proposed to alleviate this drawback by using a variable Step Size. In this paper, a new variable Step Size LMS(VSSLMS) called Categorized VSSLMS (CVSSLMS) is proposed. CVSSLMS updates the Step Size by categorizing the current status of the gradient, hence significantly improves the convergence rate. The performance of the proposed algorithm was verified from the view point of convergence rate, Excessive Mean Square Error(EMSE), and complexity through experiments.

• Economic and Environmental Geology
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• v.51 no.1
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• pp.1-13
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• 2018

The radon concentration in soil varies with environmental factors such as atmospheric temperature and pressure, rainfall and soil temperature. The effects of these factors, therefore, should be differentiate in order to analyzed the anomalous radon variation caused by earthquake events. For these reasons, a comparative analysis between the radon variations with environmental factors and the anomalous variations caused by Gyeong-ju earthquake occurred in September 12, 2016 has been conducted. Radon concentration in soil and environmental factors were continuously measured at a monitoring ste located in 58Km away from earthquake epicenter from January 01, 2014 to May 31, 2017. The co-relationships between radon concentration and environmental factors were analyzed. The seasonal average radon concentration(n) and the standard variation(${\rho}$) was calculated, and the regions of ${\pm}1{\rho}$ and ${\pm}2{\rho}$ deviations from seasonal average concentration were investigated to find the anomalous radon variation related to Gyeong-ju earthquake. Earthquake effectiveness and q-factor were also calculated. The radon concentration indicated the seasonal variation pattern, showing high in summer and low in winter. It increases with increasing air temperature and soil temperature, and has the positive co-relationships of $R^2=0.9136$ and $R^2=0.8496$, respectively. The radon concentration decreases with increasing atmospheric pressure, and has the negative co-relationships of $R^2=0.7825$. Four regions of ${\pm}2{\rho}$ deviation from average seasonal concentration (A1: 7/3~7/5, A2: 7/18, A3: 8/4~8/5, A4: 10/17~10/20) were detected before and after Gyeong-ju earthquake. A1, A2, A3 were determined as the anomalous radon variation caused by the earthquake from co-relationship analyses with environmental factors, earthquake effectiveness and q-factor. During the period of anomalous radon variation, correlation coefficients between radon concentration and environmental factors were significantly lowered compared to other periods such as air temperature ($R^2=0.2314$), soil temperature ($R^2=0.1138$) and atmospheric pressure ($R^2=0.0475$). Annual average radon concentration was also highest at 2016, the year of Gyeong-ju earthquake.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.2
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• pp.83-99
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• 2005

To evaluate environmental charateristics of the South Sea and East China Sea on summer, water and sediment quality were measured in June 2001-2003. Surface layer was affceted by Warm water originated from the high temperature and salinity-Tsushima Warm Current, on the other hand, Yellow Sea Cold Water was spread to the bottom layer in the south-western part of the Jeju island, and salinity at stations near the Yangtze River was decreased below 29psu because of a enormous freshwater discharges. Thermocline-depth was formed at about 10m, and chlorophyll maximum layer was existed in and below the thermocline. COD(Chemical Oxygen Demand), TN(Total Nitrogen), and TP(Total Phosphorus) concentrations showed seawater quality grade II in surface layer of the most area, but concentrations of such as COD, Chl. a, TSS(Total Suspended Solid), and nutrients were greatly increased in the effect area of Yangtze River discharges. Correlations between dissolved inorganic nitrogen, Chl. a and salinity were negative patterns strongly, in contrast, those of inorganic phosphorus, COD and Chl. a were positive, which indicates that phytoplankton biomass and phosphorus are considered as important factors of organic matter distribution and algal growth, respectively. in the study area. The distribution of ignition loss, COD, and $H_2S$ of surface sediment were in the ranges of 2.61-8.81%, $0.64-11.86mgO_2/g-dry$, and ND-0.25 mgS/g-dry, respectively, with relatively high concentration in the eastern part of the study area. Therefore, to effective and sustainable use and management of this area, continuous monitoring and countermeasures about major input sources to the water and sediment, and prediction according to the environmental variation, are necessary.

• Korean Journal of Environmental Biology
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• v.40 no.2
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• pp.125-137
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• 2022

To assess the characteristics of meiofaunal community fluctuations related to environmental factors, seasonal surveys were conducted in the subtidal zone of Hallyeohaesang National Park. The average depth of the study area was about 20 m, and the average water temperature at the bottom was low in winter(11.33℃) and high in summer(17.95℃). The sedimentary particles mainly comprised silt and clay at most stations. The abundance of meiofauna ranged from 81.7 to 1,296.5 Inds. 10 cm^-2, and the average abundance was 589.3 Inds. 10 cm^-2. The average abundance of meiofauna in each season was the lowest at 416.5 Inds. 10cm^-2 in winter and the highest at 704.5Inds.10 cm^-2 in spring. The dominant taxa were nematodes (about 92%) and harpacticoids (about 5%). In the cluster analysis of meiofaunal communities, they were divided into four significant groups. The largest group mainly contained spring and summer samples, and contained stations with a high nematode density of over 500 Inds. 10 cm^-2 and harpacticoids below 50 Inds. 10 cm^-2 with a high composition ratio of nematodes. In the cluster analysis, no regional division was found between the stations, and it was thought to be divided by the seasons with high abundance according to seasonal variation and the composition ratio of nematodes and harpacticoids. In the Spearman rank correlation analysis, the density of total meiofauna and the most dominant taxa, nematodes, was not significantly related to environmental factors. However, the density of harpacticoids had a significant positive correlation with water depth and a negative correlation with sediment particle size.

• Journal of Aquaculture
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• v.21 no.4
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• pp.331-338
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• 2008

Monthly changes in the gonadosomatic index (GSI) and hepatosomatic index (HSI) of wild river puffer Takifugu obscurus, and water quality environment in spawning area during breeding season were investigated from March 1995 to February 1996. Monthly changes in GSI and HSI of T. obscurus, that was cultured in low salinity, were calculated. The external morphology of the gonads, germ cell differentiation during gametogenesis and the reproductive cycle with the gonad developmental phases were investigated by histological analysis. The optimum water quality environment in Ganggyung, Choongcheongnam-do, where is spawning ground of wild T. obscurus, was $15-20^{\circ}C$ (water temperature) and 0 psu (salinity). Monthly changes in the GSI in females and males reached a maximum in May, and then rapidly decreased. Therefore, it is assumed that in the natural condition the spawning period of wild T. obscurus is May to June. In females and males, it showed a negative correlationship between the GSI and HSI. The external morphology of the gonads in female and male T. obscurus, that was cultured in low salinity, is composed of a pair of saccular structure. Based on monthly changes in the GSI, it is assumed that in female T. obscurus, that was cultured in low salinity, spawn from March through May. Therefore, it showed a negative correlationship between changes in the GSI and HSI. On the whole, in females and males, it showed a similar pattern between wild and cultured T. obscurus. The reproductive cycle with the gonad developmental phases can be classified into successive five stages in females: the early growing stage, late growing stage, mature stage, ripe and spent stage, and recovery and resting stage. In males, that can be divided into successive four stages: the growing stage, mature stage, ripe and spent stage, and recovery and resting stage. In case of wild T. obscurus, the spawning period has once a year, however, those cultured in the high water temperature ($20-27^{\circ}C$) - low salinity (under 3.3 psu) condition have reproductive characteristics having possibilities of discharge of eggs and sperms year-round as a multiple spawner.

• Economic and Environmental Geology
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• v.43 no.5
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• pp.491-503
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• 2010

Geochemical characteristics of the Moisan epithermal gold-silver deposit with total 140 samples in Haenam area, Jeollanamdo were studied by using multivariate statistical analysis (correlation analysis, factor analysis and cluster analysis). The correlation analysis reveals that Ag, Cu, Bi, Te are highly correlated with Au in the both non-mineralized and mineralized zone. It is resulted from the presence of Au-Ag bearing minerals (electrum, sylvanite, calaverite and stuezite) and non Au-Ag containing minerals (chalcopyrite, tellurobismuthite and bismuthinite). Mo shows relatively much higher correlation at the mineralized zone (0.615) than non-mineralized zone (0.269) which implies Mo content is strongly affected by Au-mineralization. While Mn, Cs, Fe, Se correlated with Au at the nonmineralized zone, they have negative correlation at the mineralized zone. Therefore, they seem to be eluviated elements from the host rock during gold mineralization. Sb is enriched during the gold mineralization showing high correlation at the mineralized zone and negative correlation at the non-mineralized zone. According to the factor analysis, Se, Ag, Cs, Te are the indicators of gold mineralization presence due to the strong affection of gold content in the non-mineralized zone. In the mineralized zone, on the other hand, Mo, Te and Sb, Cu are the indicators of gold and silver mineralization, respectively. While the cluster analysis reveals that Cd-Zn-Pb-S, Bi-Fe-Cu-Mn, Se-Te-Au-Cs-Ag, As-Sb-Ba are the similar behavior elements groups in the non-mineralized zone, Cd-Zn-Mn-Pb, Fe-S-Se, As-Bi-Cs, Ag-Sb-Cu, Au-Te-Mo are the similar behavior elements groups in the mineralized zone. Using multivariate statistical analysis as mentioned above makes it possible to compare the behavior of presented minerals and difference of geochemical characteristics between mineralized and non-mineralized zone. Therefore, it will be expected a useful tool on the similar type of mining exploration.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.3
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• pp.251-261
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• 2003

As a part of an on-going project investigating flux of materials in Gomso Tidal Flat, we have monitored temporal and spatial distribution of nitrogen components(TN, PON, DON, DIN) and have sought the relationships with the freshwater input(tidal range, salinity), the biological activities(chlorophyll-${\alpha}$, TP, DIP, silicate) and the resuspended bottom sediment in seawater(SPM) from 1999 to 2000. TN in seawater was 39.05 $\mu\textrm{m}$ol 1$\^$-1/ (31.03∼42.93 $\mu\textrm{m}$ol 1$\^$-1/) without any statistical difference(p<0.05) between the studied periods. Organic nitrogen (DON and PON) occupied 75％, 95％, 73％, and 75％ in April, August, September and November, respectively. DON and PON have been found within the narrow concentration ranges of 11.30∼16.38 $\mu\textrm{m}$ol 1$\^$-1/ and 13.16∼20.04 $\mu\textrm{m}$ol 1$\^$-1/ in spite of severe environmental differences through the studied periods. Dissolved fractions of nitrogen(DON and DIN) occupied 53∼65％ of TN. Only DIN varied with an evident temporal variability: low concentrations(1.325∼1.616 $\mu\textrm{m}$ol 1$\^$-1/) in August and high enrichment(8.377∼14.65 $\mu\textrm{m}$ol 1$\^$-1/) in September. High consumption rate of DIN by phytoplankton and a long-lasted drought probably induced such low concentration of DIN in August. Eventually heavy precipitation probably introduced plenty of new nitrogen sources into Gomso Bay in September. The portion of PON, DON and DIN in the total nitrogen was 40％, 38％ and 22％, respectively. Their contents were in the order of DON>PON>DIN for the year round except PON>DON>DIN only in September. The highest DON portion in August probably due to the active microbial decomposition of organic material in summer. Only in April, some evident negative correlations have been found between chlorophyll-${\alpha}$ and DIN mostly nitrate(-0.64, p<0.01), phosphate(-0.46, p<0.01) and silicate(-0.55, p<0.01). The Si(OH)$_4$/DIN/DIP ratios in the water column suggests the limitation of DIN for the growth of phytoplankton during the dry summer in Gomso Bay, which was the case of August in this work. Even with some difference between the studied periods, the primary factors on the distribution of nitrogen components in seawater overlying the Gomso Tidal Flat have been the tidal range and the freshwater input, but the additional variations were due to the biological activities.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.2
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• pp.78-91
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• 2015

Macrobenthic community was studied at 87 stations including intertidal and subtidal area in Yoja Bay, south coast of Korea in summer season of July 2001. Duplicate sediment samples were taken using a van Veen grab ($0.1m^2$) in each station. Mud facies of the sediments were widly distributed in the bay. And relatively high content of sand was shown in the Bulgyo-cheon stream estuary. A total of 274 species was occurred with a mean density of $2,346ind./m^2$ and a mean biomass of $78.2g/m^2$. The polychaetes were species- and density-dominant faunal group with a total of 122 species (44.5% of the total number of species), and mean density of $1,543ind./m^2$ (65.8% of the mean density). Meanwhile, molluscs were biomass-dominant faunal group with $44.4g/m^2$. Bio-Env. analysis showed that the combination of bottom salinity and sand content of the surface sediments was highly correlated to the major macrobenthic communities. The macrobenthic species number, decreasing toward inner bay from mouth of the bay, was significantly correlated to the sediment environmental variables and bottom water salinity. The spatial distribution of abundance showed significant correlation to the sand and mud contents and mean grain size of the surface sediments. Major dominant species were Minuspio japonica (polychaete) with a mean density of $1,167ind./m^2$ at upper part of the bay where salinity was low and Eriopisella sechellensis (amphipod) with $152ind./m^2$ in central part of the bay. Species diversity (H') was $3.0{\leq}$ in the mouth part of the bay and ranged 2.0-3.0 in the inner part of the bay, which showed a significant positive correlation to bottom salinity. Total number of species also showed significant correlations to the sediment composition and bottom salinity. Based on the cluster analysis the macrobenthic community of the bay was classified into five station groups from the bay mouth toward the inner part of the bay depending on the species composition. From the SIMPER analysis Minuspio japonica, Eriopisella sechellensis and Sternaspis scutata mainly contributed to the classification of station group. These results suggested that the macrobenthic communities of the bay were mainly influenced by bottom salinity together with sediment composition, and that the studies of spatial distributions of major dominant species and benthic communities should be conducted continuously to monitor the Yeoja Bay benthic environment.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.7
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• pp.387-395
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• 2015

Anaerobic mesophilic batch test of several organic wastes were carried out by a graphical statistic analysis (GSA) to evaluate their ultimate biodegradability and two distinctive decay rates ($k_1$ and $k_2$) with their corresponding degradable substrate fractions ($S_1$ and $S_2$). Each 3 L batch reactor was operated for more than 100 days at the substrate to inoculum ratio (S/I) of 0.5 as an initial total volatile solids (TVS) mass basis. Their Ultimate biodegradabilities were obtained respectively as follow; 69% swine waste, 45% dairy cow manure, 66% slaughterhouse waste, 79% food waste, 87% food waste leachate, 68% primary sludge and 39% waste activated sludge. The readily biodegradable fraction of 89% ($S_1$) of Swine Waste BVS ($S_o$) degraded with in the initial 31 days with $k_1$ of $0.116day^{-1}$, where as the rest 11% slowly biodegradable fraction ($S_2$) of BVS degraded for more than 100 days with the long term batch reaction rates ($k_2$) of $0.004day^{-1}$. For the Food Waste and Waste Activated Sludge, their readily biodegradable portions ($S_1$) appeared 89% and 80%, which degrades with $k_1$ of $0.195day^{-1}$ and $0.054day^{-1}$ for an initial 15 days and 28 days, respectively. Their corresponding long term batch reaction rates ($k_2$) were $0.003day^{-1}$ and $0.002day^{-1}$. Results from other organic wastes are addressed in this paper. The theoretical hydraulic retention times (HRTs) of anaerobic digesters treating organic wastes are easily determined by the analysis of multiple decay rate coefficients ($k_1$ and $k_2$) and their corresponding biodegradable substrate fractions ($S_1$ and $S_2$).