• Journal of Microbiology and Biotechnology
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• v.21 no.4
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• pp.341-346
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• 2011

To study the effects of salinity-sodicity on bacterial population and enzyme activities, soil samples were collected from the Bay of Yellow Sea, Incheon, South Korea. In the soils nearest to the coastline, pH, electrical conductivity ($EC_e$), sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) were greater than the criteria of saline-sodic soil, and soils collected from sites 1.5-2 km away from the coastline were not substantially affected by the intrusion and spray of seawater. Halotolerant bacteria showed similar trends, whereas non-tolerant bacteria and enzymatic activities had opposite trends. Significant positive correlations were found between EC, exchangeable $Na^+$, and pH with SAR and ESP. In contrast, $EC_e$, SAR, ESP, and exchangeable $Na^+$ exhibited significant negative correlations with bacterial populations and enzyme activities. The results of this study indicate that the soil chemical variables related with salinity-sodicity are significantly related with the sampling distance from the coastline and are the key stress factors, which greatly affect microbial and biochemical properties.

• 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.

• Asian Journal of Turfgrass Science
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• v.23 no.2
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• pp.271-278
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• 2009

This study was conducted to investigate the effect of the mixture ratio of the inorganic soil amendments on the soil physicochemical properties. In this experiment, three kinds of soil amendments which had similar pH, EC and particle size, the A, B and C, were tested. The mixture ratio of soil amendment were 0%, 3%, 5%, 7% and 10% (V/V) incorporated with sand which met to the USGA(United State of Golf Association) particle standard. To analyze the effects of amendment on chemical soil properties, pH, EC(electrical conductivity) and CEC(cation exchangeable capacity) were measured. The porosity, bulk density and hydraulic conductivity also measured to analyze the changes of physical properties. In the chemical properties, pH was significantly related to the mixture ratios of amendments, A and C(P<0.05), CEC and EC also related to the ratios of C(P<0.01). When the results were applied to the USGA standard of the soil physical properties, the optimum mixture ratios of each amendment were 3% in A and B, and 7~10% in C. To analyze the corelation of mixture ratio versus to physical character, volume of porosity was significantly related to the ratio of B (P<0.05), and showed similar corelation in porosity and hydraulic conductivity with ratio of C(P<0.05). These results indicate that types and mixture ratio of inorganic soil amendments should affect on soil physio-chemical properties of root zone on USGA sand green.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.4
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• pp.345-350
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• 1997

Characteristics of electrical conductivity(EC) of seventy one-greenhouse soil located in southern part of Korea were surveyed to obtain the basic information for sustainable management of plastic film house soils. The averaged soil EC were 5.84 and 2.49dS/m for top-and sub-soil, respectively, showing distribution of 11.3% for top-soils and 50.7% for sub-soils within the optimum level of 2.0 dS/m. On the whole, the soils with flowering plants revealed higher EC than those with fruiting vegetables showing 2.75~6.34dS/m for the former and 2.29(sub-soils)~5.13dS/m(top-soils) for the latter. In a view of soil sampling time, the soils at Feb., 1996 marked 4.3~37.7% and 10.3(top-soils)~11.3%(sub-soils) higher EC compared with the soils at Sept. and Dec., 1995, respectively. The linear regression correlation coefficients of soil minerals to EC were in oder of $Mg^{2+}$ > $NO_3{^-}$ > $Cl^-$ > $Ca^{2+}$ > $SO_4{^{2-}}$ > $K^+$ for top-soils and were $Cl^-$ > $SO_4{^{2-}}$ > $NO_3{^-}$ > $Ca^{2+}$ > $Mg^{2+}$ > $K^+$ for sub-soils. In especial, the concentration of soil EC accompanied the increasing population ratio of soil fungi to bacteria and/or actinomycetes.

• Journal of Korean Society of Forest Science
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• v.89 no.1
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• pp.55-64
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• 2000

This study was carried out to analyze the characteristics of pH and electrical conductivity(EC) at each stand and soil depth by the artificial acid rain sprinkling in the upper watershed of Mt. Palgong and furthermore to clarify the relationships between forest soil and water purification function. The results obtained in the experimental sites of Quercus acutissima and Larix leptolepis were summarized as follows ; 1. The average soil pH at each soil layer(0~5cm, 0~10cm, 0~20cm in depth) were 4.8, 4.3 and 4.5 for the Quercus acutissima soil and 5.15, 5.19 and 5.21 for the Larix leptolepis soil. The soil pH of Larix leptolepis stand was higher than that of Quercus acutissima stand. In addition, the deeper soil depth was, the higher soil pH was. 2. The soil solution pH of Larix leptolepis stand was higher than that of Quercus acutissima stand. It was due to the high soil pH of Larix leptolepis stand itself and the difference of humus layer thickness. 3. It took time to show the pH buffer capacity of forest soil after application of artificial acid rain in the forest soil. The pH value of soil solution in each experimental site was maximum at this time and then did not increase pH value any more. 4. Soil solution EC increased slowly with pH 3.0 treatment, but it decreased slowly with pH 5.0 treatment over time. It was assumed that the amount of the leached cation and the ions leading buffer action changed at the stands with ranges of acidity treatment. 5. From the trend of soil solution EC at each soil depth, it seemed that the water buffer capacity of the forest soil increased as the soil depth increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.733-738
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• 1998

본 논문에서는 고체 리듐 전지를 개발하기 위하여 poly(ethylene oxide) [PEO] 에 $LiClO_4$, poly (vinylidene fluoride) [PVDF] 및 가소제로 propylene carbonate [PC] 와 ethylene carbonate[EC] 등을 혼합여 고분자 저해질을 제조하였다. 또한 고체 리듐 전지용 정극으로써 우수한 특성이 기대되는 $Li_xV_3O_8$을 졸-겔법에 의해 합성하여 $Li_xV_3O_8$SPE/Li cell 의 전기화학적 특성을 측정하였다. 고분자 matrix는 PEO와 PVDE를 혼합 사용한 결과 $PEO_4 PVDF_4LiCIO_4PC_5EC_5$ 고분자 전해질이 상온에서 $5.2 {\times} 10{-3}$ S/cm 의 높은 이온 전도도를 나타냈으며 리듐 이온 transference number는 0.3이었다. 졸-겔법에 의해 제조된 $Li_xV_3O_8$을 사용한 $Li_xV_3O_8$SPE/Li cell의 방전시 cell 저항이 방전 초기에는 비소한 증가를 하다가 방전 말기 전압인 2.0V에서 크게 증가하였다. $Li_xV_3O_8$ composite 정극의 첫 번째 방전 용량은 295㎃h/g이었으며 8번째 충방전 싸이클부터 방전 용량이 안정화 되었고 15번째 방전 용량도 212㎃h/g으로 고체 전지용 정극으로써 우수한 특성을 보였다.

• Korean Journal of Remote Sensing
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• v.36 no.6_3
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• pp.1733-1741
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• 2020

This study analyzed the effect of meteorological factors on the concentration of PM10 (particulate matter 10) in the atmosphere and the variation of rainwater quality using multivariate statistical analysis. The concentration of PM10 in the atmosphere was continuously measured during eleven precipitation events with a custom-built PM sensor node. A total of 183 rainwater samples were analyzed for pH, EC (electrical conductivity), and water-soluble cations (Na+, Mg2+, K+, Ca2+, NH4+) and anions (Cl-, NO3-, SO42-). The data has been analyzed using two multivariate statistical techniques (principal component analysis, PCA, and Pearson correlation analysis) to identify relationships among PM10 concentrations in the atmosphere, meteorological factors, and rainwater quality factors. When the rainfall intensity was relatively strong (> 5 mm/h, rainfall type 1), the PM10 concentration in the atmosphere showed a negative correlation (r = -0.55, p < 0.05) with cumulative rainfall. The PM10 concentration increased the concentration of water-soluble ions (r = 0.25) and EC (r = 0.4), and decreased the pH (r = -0.7) of rainwater samples. However, for rainfall type 2 (< 5 mm/h), there was no negative correlation between the PM10 concentration in the atmosphere and cumulative rainfall and no statistically significant correlation between the PM10 concentration in the atmosphere and rainwater quality.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.76-79
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• 1996

Polypyrrole films were electrochemically synthesized under a constant current condition ranging from 50 ${\mu}$A/$\textrm{cm}^2$ to 2 mA/$\textrm{cm}^2$ with resultant high electrical conductivity about 100 S/cm. Specific energy of 70 Wh/kg and Ah efficiency of 97% were achieved during the cycling using liquid electrolyte system. On the other hand, consequences of the cycling were 51 Wh/kg and 95% using PEO$\sub$8/LiClO$_4$PC$\sub$5/EC$\sub$5/ solid electrolyte system. Polypyrrole film can be cycled stable and Ah efficiency is excellent, so it can be applicable to the cathode of Lithium secondary batteries.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.519-523
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• 2006

$LiFePO_4$ has been received attention as a potential cathode material for the lithium secondary batteries. In our study, $LiFePO_4$ cathode active materials were synthesized by a solid-state reaction. It was modified by coating $TiO_2$ and carbon in order to enhance cyclic performance and electronic conductivity. $TiO_2$ and carbon coatings on $LiFePO_4$ materials enhanced the electronic conductivity and its charge/discharge capacity. For lithium polymer battery applications, $LiFePO_4$/solid polymer electrolyte (SPE)/Li and $LiFePO_{4}-TiO_{2}/SPE/Li$ cells were characterized by a cyclic voltammetry and charge/discharge cycling. The electrode with $LiFePO_{4}-carbon-TiO_{2}$ in PVDF-PC-EC-$LiClO_{4}$ electrolyte showed promising capacity of above 100 mAh/g at 1C rate.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.385-391
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• 2019

In the present study, vanadium oxide($V_2O_5$) films for electrochromic(EC) application are fabricated using sol-gel spin coating method. In order to optimize the EC performance of the $V_2O_5$ films, we adjust the amounts of polyvinylpyrrolidone(PVP) added to the solution at 0, 5, 10, and 15 wt%. Due to the effect of added PVP on the $V_2O_5$ films, the obtained films show increases of film thickness and crystallinity. Compared to other samples, optimum weight percent(10 wt%) of PVP led to superior EC performance with transmittance modulation(45.43 %), responding speeds(6.0 s at colored state and 6.2 s at bleached state), and coloration efficiency($29.8cm^2/C$). This performance improvement can be mainly attributed to the enhanced electrical conductivity and electrochemical activity due to the increased crystallinity and thickness of the $V_2O_5$ films. Therefore, $V_2O_5$ films fabricated with optimized amount of PVP can be a promising EC material for high-performance EC devices.