• The KIPS Transactions:PartB
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• v.13B no.4 s.107
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• pp.369-376
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• 2006

The degradation and its inverse modeling can achieve restoration of corrupted image, caused by scaled digitization and electronic transmission. De-speckle process on the noisy document(or SAR) images is one of the basic examples. Non-linearity of the speckle noise model may hinder the inverse process. In this paper, our study is focused on investigation of the restoration methods for bi-level document image degraded by the impulse noise model. Our study shows that, on bi-level document images, the weighted-median filter and the Lee filter methods are very effective among other spatial filtering methods, but wavelet filter method is ineffective in aspect of processing speed: approximately 100 times slower. Optimal values of the weight to be used in the weighted median filter are investigated and presented in this paper.

• The Korean Journal of Malacology
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• v.24 no.3
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• pp.175-188
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• 2008

This study was performed to describe the influence of water temperature and salinity on the filtration rate of the hard clam, Meretrix petechialis. The filtration rates of hard clams showed significant differences depending on both water temperature and age group (two-way ANOVA, p < 0.001). The filtration rate of all the hard clams, aged from 1 to 4 years, was generally reduced in low temperature range ( $5-15^{\circ}C$). As the water temperature increased, the filtration rate increased exponentially. The filtration rate was relatively high in $20-30^{\circ}C$ water temperature range, but rapidly decreased again at around $35^{\circ}C$. Variations in the data for filtration rates of hard clams, relative to age and changing water temperature, were used to determine the temperature coefficient $Q_{10}$ in each water temperature range. In $5-15^{\circ}C$ temperature range, every age group showed the highest $Q_{10}$ figure. It was found that on the whole, the higher the water temperature was, the lower the number of $Q_{10}$ was. Regardless of age, the number of $Q_{10}$ was higher in the lower water temperature range. In $25-35^{\circ}C$ temperature range, the number of $Q_{10}$ was less than 1.00 in all age groups, implying that this is the range in which the filtration rate decreased. Variations in the filtration rate also showed very clear differences (two-way ANOVA, p < 0.001) according to changing salinity and age. All the age groups, from 1 to 4 year olds, showed low filtration rates at both low salinity (10-15 psu) and high salinity (40 psu). The highest filtration rate was recorded at 30 psu, and relatively high filtration rates were found around 30 psu. However, the Student-Newman-Keuls post hoc multiple comparison test found that the hard clams in the 1-year group showed high filtration rates in a relatively narrower salinity range compared to those in the 2, 3, and 4 year groups. In other words, hard clams in the 2, 3, and 4 year groups showed high filtration rates at higher levels of salinity.

• Journal of Aquaculture
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• v.12 no.1
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• pp.47-56
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• 1999

Denitrification by anaerobic bacteria is one of the most common processes of removing nitrate from recirculating aquaculture systems. This process is affected by many factors such as external carbon sources, hydraulic retention time (HRT), and $COD/NO_3-N$ ratio. Although external organic carbon sources are essential for the denitrification process, these also contribute to increase dissolved organic carbon concentration in recirculating aquaculture systems. So these external organic carbons must be removed from the systems. This study was conducted to find out the optimum operating conditions for the removal of external organic carbons in a submerged denitrification biofilter. Combinations of two external carbon sources (glucose and methanol), two HRT (4- and 8-hour), and four different C:N ratios (3, 4, 5, and 6) were used in this experiment. The removal efficiencies of organic carbon sources at 8-hour HRT were always better than those at 4-hour's (P<0.05). Maximum removal efficiencies were achieved when C:N ratio was 5 in both glucose and methanol. The removal efficiencies of methanol were always better than those of glucose. The maximum removal efficiencies of glucose and methanol were 76.5% and 84.0%, respectively and the removal rates were 223.5 $g/m^2/day$ and 247.1$g/m^2/day$. The maximum removal rates of glucose (290.9 $g/m^2/day$) and methanol (355.6 $g/m^2/day$) were achieved at 4-hour HRT and 5 C:N ratio. But the concentrations of SCOD in the effluent of both glucose ($52.5 mg/\ell$) and methanol ($40.9 mg/\ell$) were too high for rearing fish. Therefore, the optimum operating conditions for the removal of external carbon in a submerged denitrification biofilter were 8-hour HRT and 5 C:N ratio. And methanol showed better efficiency as an external carbon sources.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.405-407
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• 1997

본 논문은 자동차 번호판 용도문자를 인식하개 위한 전처리 과정으로써 웨이브릿 변환을 적용한 연구에 관해 기술한다. 웨이브릿 변환에 의하여 여과된 고주파 대역의 영상은 수평방향, 수직방향, 대각선 방향의 윤관석 형태로 세 개의 대역에 존재하게 되는데, 대상영상이 고주파 대역의 에너지량이 적게 나타나는 반면에 저주파 대역의 에너지량은 크므로 용도문자의 인식 과정에서 저주파 대역 부분만을 이용하였다. 저주파 대역에서 $20{\times}20$크기의 영상을 추출하고 영상을 정규화 하여 오츠알고리즘을 통한 이치화 과정을 거친 다음 역전파 신경망으로 인식함으로써 기존의 단순축소 방법보다 향상된 결과를 실험을 통하여 확인할 수 있었다.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.406-413
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• 2012

Effect of three additives, chitosan, ferric chloride, and MPE50 on membrane fouling reduction was studied. They were introduced with various dosing rate into activated sludge, and changes in filtration resistance measured by the batch cell filtration test were evaluated. Both the filtration resistance and the specific cake resistance were minimized at 20 mg/g-MLSS with chitosan, 70 mg/g-MLSS with ferric chloride, and 20 mg/g-MLSS with MPE50 addition, respectively. Introduction of the additives into the activated sludge resulted in reduction of not only cake resistance, but also fouling resistance. However, the chitosan addition to three different activated sludge resulted in three different optimal dose of 10, 20, 30 mg/g-MLSS, respectively. This implies that the optimal dose is dependent on sludge characteristics rather than a constant value. Overdose above the optimal dosage always aggravated filterability in all cases. Zeta potential of sludge flocs, relative hydrophobicity, floc size distribution, soluble EPS concentration and supernatant turbidity were measured in order to analyze fouling reduction mechanism. Nearly neutral surface charge along with the largest particle size was observed at the optimal dose. This could be explained by particle destabilization and restabilization mechanism as positively charged additives were injected into sludge flocs of negative surface charge. Both soluble EPS concentration and supernatant turbidity also showed the lowest value at the optimal dose. These foulants are believed to be coagulated and entrapped in sludge flocs during flocculation. Chitosan and MPE50 which are cationic polymeric substances showed higher reduction in both soluble EPS and fine particles comparing with ferric chloride.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.12
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• pp.2012-2018
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• 2013

The objective of this research was to investigate the quality characteristics of the spirits by different distillation and filtrations. The contents of alcohol, total acids, and amino acids in rice mash were 15%, 0.25 g/100 mL, and 0.15 g/100 mL, respectively. The soluble content was $10^{\circ}Brix$, and pH was 4.6 in the rice mash. Lactic acid was the most prominent organic acid found in rice mash. The rice spirit distilled by a multi stage distiller showed the highest amounts of aroma compounds, such as fusel oil and esters. However, the filtration did not affect the amounts of total aroma compounds. It is suggested that a multi stage distiller may influence taste and flavor positively by enhancing the aroma and removing the impurities in rice spirits.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.12
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• pp.1304-1309
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• 2006

In this study, removal efficiencies of treatment processes with C. tracer which is similar to the characteristics of Cryptosporidium were investigated. The highest removal efficiency of C. tracer was 97.16% when the input dose of PACI(Poly aluminium chloride, $Al_2O_3$(10%)) was 10 mg/L. The higher turbidity and SS removal efficiencies were, the more C. tracer cohesion efficiency increased. Also when pH of the raw water was high, removal efficiency of C. tracer increased. As the correlationship($R^2$) between effluent turbidity after coagulation-precipitation and removal efficiency of C. tracer was 0.9506, removal efficiency of Cryptosporidium could be evaluated by effluent turbidity after coagulation-precipitation. Also the range of C. tracer removal efficiency by sand filtration was $94.00{\sim}95.83%$ and the correlationship($R^2$) between effluent turbidity after filtration and removal efficiency of C. tracer was 0.8704. Therefore, when filtration-effluent turbidity is good under the optimized coagulation condition, removal efficiencies of Cryptosporidium by coagulation-precipitation, sand rapid filtration and sand rapid filtration after coagulation-precipitation are estimated as 1.55 log(97.16%), 1.38 log(95.83%) and 2.31 log(99.51%) respectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.3
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• pp.235-243
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• 2006

In this study, an experimental study on the sorption properties of uranium(VI) onto a bentonite colloid generated from Gyeongju bentonite which is a potential buffer material in a high-level radioactive waste repository was performed as a function of the pH and the ionic strength. The bentonite colloid prepared by separating a colloidal fraction was mainly composed of montmorillonite. The concentration and the size fraction of the prepared bentonite colloid measured using a gravitational filtration method was about 5100 ppm and 200-450 nm in diameter, respectively. The amount of uranium removed by the sorption reaction bottle walls, by precipitation, and by ultrafiltration was analyzed by carrying out some blank tests. The removed amount of uranium was found not to be significant except the case of ultrafiltration at 0.001 M $NaClO_4$. The ultrafiltration was significant in the lower ionic strength of 0.001 M $NaClO_4$ due to the cationic sorption onto the ultrafilter by a surface charge reversion. The distribution coefficient $K_d$ (or pseudo-colloid formation constant) of uranium(VI) for the bentonite colloid was about $10^4{\sim}10^7mL/g$ depending upon pH and ionic strength of $NaClO_4$ and the $K_d$ was highest in the neutral pH around 6.5. It is noted that the sorption of uranium(VI) onto the bentonite colloid is closely related with aqueous species of uranium depending upon geochemical parameters such as pH, ionic strength, and carbonate concentration. As a consequence, the bentonite colloids generated from a bentonite buffer can mobilize the uranium(VI) as a colloidal form through geological media due to their high sorption capacity.

• Journal of the Korea Society for Simulation
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• v.20 no.3
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• pp.69-78
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• 2011

A large-scale sensor network usually operates in open and unattended environments, hence individual sensor node is vulnerable to various attacks. Therefore, malicious attackers can physically capture sensor nodes and inject false reports into the network easily through compromised nodes. These false reports are forwarded to the base station. The false report injection attack causes not only false alarms, but also the depletion of the restricted energy resources in a battery powered network. The statistical en-route filtering (SEF) mechanism was proposed to detect and drop false reports en route. In SEF, the choice of routing paths largely affect the energy consumption rate and the detecting power of the false report. To sustain the secure routing path, when and how to execute the path re-selection is greatly need by reason of the frequent network topology change and the nodes's limitations. In this paper, the regional path re-selection period determination method is proposed for efficient usage of the limited energy resource. A fuzzy logic system is exploited in order to dynamically determine the path re-selection period and compose the routing path. The simulation results show that up to 50% of the energy is saved by applying the proposed method.

• Journal of the Korea Society for Simulation
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• v.20 no.4
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• pp.31-40
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• 2011

Sensor nodes are easily exposed to malicious attackers by physical attacks. The attacker can generate various attacks using compromised nodes in a sensor network. The false report generating application layers injects the network by the compromised node. If a base station has the injected false report, a false alarm also occurs and unnecessary energy of the node is used. In order to defend the attack, a statistical en-route filtering method is proposed to filter the false report that goes to the base station as soon as possible. A path renewal method, which improves the method, is proposed to maintain a detection ability of the statistical en-route filtering method and to consume balanced energy of the node. In this paper, we proposed the secure path cycle method to consume effective energy for a path renewal. To select the secure path cycle, the base station determines through hop counts and the quantity of report transmission by an evaluation function. In addition, three methods, which are statistical en-route filter, path selection method, and path renewal method, are evaluated with our proposed method for efficient energy use. Therefore, the proposed method keeps the secure path and makes the efficiency of energy consumption high.