• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.3
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• pp.473-483
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• 2012

To achieve an entire end-to-end security, the classical authentication setting such that all participants have a same password is not practical since a password is not a common secret but a personal secret depending on an individual. Thus, an efficient client to client different password-based authenticated key agreement protocol (for short, EC2C-PAKA) has been suggested in the cross-realm setting. Very recently, however, a security weakness of the EC2C-PAKA protocol has been analyzed by Feng and Xu. They have claimed that the EC2C-PAKA protocol is insecure against a password impersonation attack. They also have presented an improved version of the EC2C-PAKA protocol. In this paper, we demonstrate that their claim on the insecurity of EC2C-PAKA protocol against a password impersonation attack is not valid. We show that the EC2C-PAKA protocol is still secure against the password impersonation attack. In addition, ironically, we show that the improved protocol by Feng and Xu is insecure against an impersonation attack such that a server holding password of Alice in realm A can impersonate Bob in realm B. We also discuss a countermeasure to prevent the attack.

• Horticultural Science & Technology
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• v.31 no.2
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• pp.173-178
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• 2013

Experiments were conducted to investigate the optimum concentration of nutrient solution for strawberry 'Maehyang' bred domestically for exportation in hydroponics. Nutrient solutions for strawberry, which was made by Yamazaki, were supplied electrical conductivity (EC) 0.6, 0.8, 1.2, and $1.8dS{\cdot}m^{-1}$ after planting on cocopeat medium during the experiment period. Growth of shoot of strawberries did not show any statistical differences among treatments. Fruit length showed the longest in EC 0.8 and $1.2dS{\cdot}m^{-1}$, followed by 0.6 and $1.8dS{\cdot}m^{-1}$ in the first and third cluster. It showed the shortest in EC $1.8dS{\cdot}m^{-1}$ in the second cluster but there were no significant differences among treatments in the fourth cluster. Fruit diameter did not show significant differences among treatments in the first and second cluster but was the longest in the lowest concentration EC $0.6dS{\cdot}m^{-1}$ in the third cluster. The shortest was in EC $1.8dS{\cdot}m^{-1}$ in the fourth cluster. The heaviest mean fruit weight appeared in EC 0.8 and $1.2dS{\cdot}m^{-1}$, and the lightest was in EC $1.8dS{\cdot}m^{-1}$ in the first cluster and also lightest in EC $1.8dS{\cdot}m^{-1}$ but no significant differences was found among other treatments in the second & third cluster. Also the fruit weight was significantly light in plants grown in EC $1.8dS{\cdot}m^{-1}$ than $0.6dS{\cdot}m^{-1}$ in the fourth cluster. Soluble solids content of fruit was the highest in EC $0.6dS{\cdot}m^{-1}$ in all cluster. As a result, we came to the conclusion that the optimum EC for strawberry 'Maehyang' was EC 0.8 - $1.2dS{\cdot}m^{-1}$ during low temperature season. This result will be utilized as an indicator for strawberry hydroponics.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.6
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• pp.398-404
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• 2000

We examined the effect of soil:water ratio on the equivalent concentration of individual electrolyte species and the electrical conductivities (EC) of the diluted extracts of 24 soil samples (loam or silt loam) collected from rose-cultivated plastic houses to estimate the EC of saturated soil-paste extracts (ECe) from diluted soil extracts. With increasing volume ratio of water (higher dilution), the equivalent concentrations of each electrolyte species and their sum increased. The relative contribution to the EC, however, was highest for $NO_3{^-}$, irrespective of soil:water ratio. The measured ECe was 6.36 for loam and $8.09dS\;m^{-1}$ for silt loam soils and the corresponding soil:water ratio was 0.38 and 0.50, respectively. The EC_e estimated from the EC of diluted extracts at 1:1, 1:2, or 1:5 soil:water ratios using their corresponding uniform diluted factors was lower than the measured EC_e and this difference was greater with higher dilution and EC values. Therefore, the alternative diluted factors (y) for each soil: water ratio were obtained following the definition of diluted factor and were correlated significantly with volume ratios of added water (x): y=1.55x+0.5 for loam and y=1.21x+0.48 for silt loam soils. On the other hand, correlation analyses of the EC of soil extracts (y) to the volume ratio of added water (x) on log-log scale yielded linear models: logy = -0.805logx + logb, SD of slope=0.05, b=sample specific constant, n=24). With known saturation percentage of a sample representing a group and and the EC of diluted extract of a given soil, the EC_e could be predicted using the proposed logarithmic equation.

• Horticultural Science & Technology
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• v.29 no.1
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• pp.29-35
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• 2011

Individual ion concentrations and ionic contributions to EC reading in the circulated nutrient solution are the important factors to be considered for stable EC-based closed-loop soilless culture. This study was conducted to determine appropriate ion-analysis intervals of the circulated nutrient solutions based on ion concentration, ion balance, and ion electrical conductivity under different renewal intervals in EC-based nutrient control systems for sweet peppers (Capsicum annum L. 'Fiesta') in early growth stage. Average node numbers of the plants were 13 and 18 when the experiment started and finished, respectively, and three plants were grown in each rockwool slab. Four different renewal intervals of circulated nutrient solutions such as 1, 2, 3, and 4 weeks were used as treatment. Nutrient solutions were supplied to the plants based on integrated radiation. Drainage was collected into drain tanks after irrigation ended in the day and then mixed with fresh water until the EC reaches 2.69 $dS{\cdot}m^{-1}$. The replenished nutrient solution was supplied to the plants in the next day. Ion concentrations of the individual ions periodically analyzed in the circulated nutrient solutions showed no significant differences among the treatments during the experimental period. Ion concentrations of $K^+$, $Ca^{2+}$, $Mg^{2+}$, $Na^+$, $NO_3{^-}$, ${SO_4}^{2-}$, ${PO_4}^{3-}$, and $Cl^-$ varied within 5-8, 11-14, 2.0-2.7, 0.5-0.6, 14-19, 4-5, 1-4, and 0.3-0.5 $meq{\cdot}L^{-1}$, respectively. Ion balance showed a consistent tendency over all the treatments and especially $K^+$ : $Ca^{2+}$ and ${SO_4}^{2-}$ : ${PO_4}^{3-}$ played great roles in the cation and anion balances in the nutrient solutions, respectively. Activity coefficients of ions such as $K^+$, $NO_3{^-}$, and $H_2PO_4{^-}$ varied within 0.8-0.9 and those of $Ca^{2+}$, $Mg^{2+}$, ${SO_4}^{2-}$ varied within 0.5-0.6, showing little changes with time. Ionic contributions of $K^+$ and $NO_3{^-}$ to EC reading were the greatest followed by $Ca^{2+}$, ${SO_4}^{2-}$, and $Mg^{2+}$ in the order. From the results, we thought that allowable ranges in ion concentration, ion balance, and subsequent individual ionic contributions to EC reading would be obtained within 4-week renewal interval of nutrient solution in EC-based closed-loop soilless culture for sweet pepper plants.

• Korean journal of applied entomology
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• v.11 no.1
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• pp.37-40
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• 1972

Experiments were carried out to control white-tip nematode, Aphelenchoides besseyi Christie, during the period just before transplanting. The experimental results were summarized as fellows: 1: From a 12-hr to a 24-hr sled-soaking application into 500 times dilutions of Malathion $80\%$ Ec, Sumithion $50\%$ EC and Lebaycid $50\%$ EC were highly effective than other emulsifierble concentrations of chemicals. 2) The water surface application of PSP-204 $5\%$ G, Diazinon $3\%$ G, Nemagon $20\%$ G and Terracurr-P $5\%$ G were effective. 3: Root·dipping application of Sumithion $50\%$ Ec, Lebaycid $50\%$ Ec and Nemagon $80\%$ Ec were more effective chemicals than others.

• KSBB Journal
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• v.15 no.3
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• pp.299-306
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• 2000

Concern for the effects of toxic chemicals on the environment leads the search for better bioassay test organisms and test procedures. Photobacterium phosphoreum was used successfully as a test organism and the luminometer detection technique was an effective and simple method for determining the concentration of toxic chemicals. With EC50 a total of 14 chlorine substituted phenols benzenes and ethanes were used for the experiments. The test results showed that the toxicity to P. phosphoreum increased in the order of phenol > benzene > ethane and the toxicity also increased with the number of chlorine substitution. Quantitative structure activity relationship (QSARO) model can be used to predict EC50 to save time and endeavor. Correlation was well established with the QSAR parameters such as log P, log S and solvatochromic parameter(Vi/100 $\pi$, ${\beta}$m and am). The QSAR modeling was used with multi-regression analysis and mono-regression analysis. These analyses resulted in the following QSAR : $log EC_{50} =2.48 + 0.914 log S(n=9 R2=85.5% RE=0.378) log EC_{50}=0.35 - 4.48 Vi/100 + 2.84 \pi^* +9.46{\beta}m-4.48am (n =14 R2=98.2% RE=0.012) log EC_{50} =2.64 -1.66 log P(n=5, R2=98.8% RE=0.16) log EC_{50}=3.44 -1.09 log P(n=9 R2= 80.8% Re=0.207)$

• Horticultural Science & Technology
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• v.29 no.1
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• pp.23-28
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• 2011

Experiments were conducted to investigate the optimum concentration of the nutrient solution in strawberry 'Sulhyang' with hydroponics in relationship between root activity and nutrient concentrations. Nutrient solutions for strawberry, made by Yamazaki, were supplied EC 0.5, 1.0, 2.0 $dS{\cdot}m^{-1}$ during experiment period. Growth of shoot and root of strawberries grown in visible plastic pot was observed during experiment. Petiole length was longest in plants grown in EC 1.0 $dS{\cdot}m^{-1}$, followed by 2.0 and 0.5 $dS{\cdot}m^{-1}$. Leaf width was longest in plants grown in EC 1.0 $dS{\cdot}m^{-1}$, followed by 0.5 and 2.0 $dS{\cdot}m^{-1}$. Fruit length, fruit diameter, fruit weight and yield were higher in EC 0.5 and 1.0 $dS{\cdot}m^{-1}$ than 2.0 $dS{\cdot}m^{-1}$ treatment but, soluble solids of the fruit did not show statistical differences among treatments. Shoot dry weight was heaviest in EC 1.0 $dS{\cdot}m^{-1}$, followed by 0.5 and 2.0 $dS{\cdot}m^{-1}$. Root dry weight was heavier in EC 0.5 and 1.0 $dS{\cdot}m^{-1}$ but significantly light in 2.0 $dS{\cdot}m^{-1}$. pH of the drainage solution was elevated in low nutrient concentration and lowered in high concentration. Also root activity was high in low nutrient concentration and low in high concentration. As a result, the optimum EC for strawberry 'Sulhyang' was EC 1.0 $dS{\cdot}m^{-1}$ in this experiment. It was confirmed that there was high relationship between root activity and pH of drainage solution. This result will be utilized as an indicator for strawberry hydroponics.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.4
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• pp.360-364
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• 1996

Study on germination ratio and growth of lettuce affected by accumulated salt in vinyl house cultivation soils was investigated by pot test with EC 1.65. 3.50, 5.75. 7.15. 9.50 and 13.57 dS/m. (Germination rate of lettuce in different electric conductivity of 0, 2, 4, 6, 8 and 10 dS/m controlled with KCl were 96.7, 96.7, 87.8, 82.2, 52.2, and 27.8 % respectively. Standing ratio of lettuce in soil below 6 dS/m was more than 60% and in soils of 7.15, 9.50 and 13.57 dS/m they were 45, 32 and 31%, respectively. Growth and fresh weight of lettuces increased significantly in a low EC content soil. The fresh weight of lettuces in the soil of EC 3.50 dS/m was higher than that of the soil EC 1.65 dS/m by 22%, while another soils(EC: 5.75, 7.15, 9.50 and 13.57 dS/m) were decreased 3, 15, 60 and 62%, respectively. Relationship between soil EC and standing ratio of lettuce showed high correlation coefficient($r=-0.9057^{**}$). Therefore, in the field of vinyl houses concentrated salt, standing ratio of lettuce can be foreseen by soil EC [Y = -4.313x+ 82.95 (Y:standing ratio, x:soil EC)], also standing ratio and fresh weight of lettuce showed high correlation coefficient($r=0.8396^{**}$).

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.1
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• pp.21-31
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• 2016

Organic carbon (OC) and elemental carbon (EC) in $PM_{2.5}$ were measured with Sunset OC/EC Field Analyzer at Taehwa Research Forest (TRF) near Seoul metropolitan area from May 2013 to April 2014. During the study period, the mean concentrations of OC and EC were $5.0{\pm}3.2{\mu}gC/m^3$ and $1.7{\pm}1.0{\mu}gC/m^3$, respectively. They showed clear seasonality reaching their maximum in winter ($6.5{\mu}gC/m^3$ and $1.9{\mu}gC/m^3$) and minimum in wet summer ($2.5{\mu}gC/m^3$ and $1.4{\mu}gC/m^3$). While OC showed greater seasonal variation, the diurnal variation was more noticeable for EC through all seasons with a clear maximum in the morning, which reveals the influence of vehicle emissions. In contrast, OC exhibited a broad second peak in the afternoon during May~June, when biological activities were the highest. Using the morning peaks of EC and OC, primary OC/EC ratio was assessed, which was assumed to be anthropogenic origin. It was the greatest in winter followed by spring and the lowest in wet summer. The seasonal difference in primary OC/EC ratio implies the influence of non-local sources of OC at the Mt. Taehwa.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.555-562
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• 2010

For the rapid and reliable detection of toxic compounds in water, a novel toxicity detection methodology based on sulfur-oxidizing bacteria (SOB) has been developed. The methodology exploits the ability of SOB to oxidize elemental sulfur to sulfuric acid in the presence of oxygen. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH. Using a synthetic stream water (EC=0.12 mS/cm and pH=7.2), the baseline steady-state EC and pH values were 0.5~1.2 mS/cm and ~2.5 over 7 days of testing at HRT 30 minutes. When nitrite compounds were added to the system, the effluent EC decreased and the pH increased due to the inhibition of the SOB. Optimum HRT was 30 min and this HRT could be decresed by using smaller sulfur particles.