• Journal for History of Mathematics
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• v.18 no.2
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• pp.117-126
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• 2005

In this paper, we analyze the basic concepts of permutation polynomials over finite fields, and the historical background through the use of the major classes of permutation polynomials over the fields. And also, we find a method of the polynomial representation with respect to cycles on the fields.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.3
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• pp.179-188
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• 1994

This study was conducted to investigate the distribution of potassium fractions and to establish the soil chemical indices for assessing potassium availability in upland soil. Soil samples were collected from 66 vegetable crop fields of Chungbuk Jungweon, Jeonbuk Imsil and Kyengbuk Euiseong and these samples were analyzed water soluble(W. S. -K), exchangeable(Exch. -K) and nonexchangeable potassium(Nonex. -K). The distribution of potassium fractions was examined for soils having different physico-chemical properties and compared with the soil parameters related to the potassium availability. 1. The distribution ranges of W.S.-K, Exch.-K and Nonex.-K were 0.07~1.42, 0.27~2.30, and 0.84~4.74me/100g, and average contents of relevent fractions were 0.40, 1.03 and 2.37me/100g respectively. 2. Contents of W.S.-K and Exch.-K were decreased with increasing soil pH, CEC, Exch. Ca and Exch. Mg contents but Nonex. -K showed a low correlationship with these factors. 3. Exch.-K content slightly inereased with increasing clay content, while W.S.-K and Nonex. -K contents were grandually decreased with clay contents. 4. The relationship between W.S.-K and Exch.-K was significant and W.S.-K was released from soil at 0.23me/100g content of Exch.-K 5. Contents of W.S-K and Exch.-K showed high correlationship with soil chemical parameters such as ratio of exchangeable cations(K/Ca+Mg), ratio of exchangeable cation equivalent[$K/{\sqrt{Ca+Mg}}:(me/100g)^{1/2}$], potassium exchangeable free energy(${\Delta}F=RT$ 1n $K/{\sqrt{Ca+Mg}}$ : calories/mole) and saturation percentage of potassium($Exch.K/CEC{\times}100$), and these factors were considered to be good parameters for assessing soil potassium availability.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.61-71
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• 2003

On the soft soil consisted of silty clay, the compulsion replacement method is useful for revetment and its safety is very much affected by compulsion replacement depth. Usual method calculating the compulsion replacement depth on silty clay is considered the bearing capacity of soft soil with undrained shear strength increase from ground surface and weight of revetment. But according to soil deposit, there are some cases of soft soil with inter sand layer or clayed silt, which affect the compulsion replacement depth. In this paper, the compulsion replacement depth on soft soil with inter sand layer is analyzed by layered weighted average bearing capacity considering influence effect of Perloff et al.(1967) and compared with numerical method(FLAC). In the result, the calculated depth from numerical method is nearest to layered weighted average bearing capacity in case that contact width under revetment is $0.2B_o$(soft soil with inter sand layer), $0.5B_o$(only soft soil) and the effect of contact width under revetment is less than undrained shear strength, thickness and location of inter sand layer. Also the compulsion replacement depth is as much as the inter sand thickness($d_2/B_o$) is thinner, the inter sand layer location($d_1/B_o$) is farther, and undrained shear strength is less.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.129-136
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• 2010

This study is to investigate experimentally the engineering characteristics of cement mortar according to the replacement method and contents of recycled aggregate powder (RP) by collecting the recycled aggregate powder with the maximum size of below 0.08 mm and 0.15 mm. then, the results of the study can be summarized as follows. The flow of flesh mortar represented a trend in decreasing while the recycled aggregate powder was substituted as it is compared with that of plain. In addition, in case of correlation between tests, it appeared that the correlation between flow and ring flow is big. In the case of the characteristics of hardened mortar, the strength showed more improvements as the RP was substituted to aggregate than the case, which is substituted to aggregate. In addition, it was verified that the results in which the RP was substituted to aggregate by 5% represented similar values to that of the plain according to the passage of age.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.2
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• pp.93-100
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• 2013

A variety of researches on the concrete with high volume mineral admixture have increased in recent years. In fact, it is very important to find appropriate replacement ratio of concrete with high volume mineral admixture in order to apply in the field. In this study, compressive strength according to fly ash and blast furnace slag replacement ratio as well as curing temperature was measured in the conditions of obtaining the same workability in order to examine the characteristics of concrete with high volume mineral admixture. In conclusion, it was found that the compressive strength at the age of 3 days decreased by 1.4MPa and the compressive strength at the age of 28 days decreased by 3.8MPa when the fly ash replacement ratio increased by 10%. Also, it was found that the compressive strength at the age of 3 days decreased by 1.0MPa and the compressive strength at the age of 28 days decreased by 0.9MPa when the blast furnace slag replacement ratio increased by 10%. Through the tests, we obtained the basic data for developing the future research on the concrete with high volume mineral admixture for housing structure.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.3
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• pp.246-252
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• 1998

A survey was conducted to investigate the status of soils involving pH, electrical conductivity, total organic matter content, available phosphate and major exchangeable cations in the paddy soils sampled from 1,168 sites throughout the country. The content of soil chemical properties was lower on the average than the optimum levels for cropping. An average value showed pH 5.6, organic matter $25g\;kg^{-1}$, available phosphate $128mg\;kg^{-1}$, available silicate $72mg\;kg^{-1}$, and exchangeable potassium and the calcium and magnesium were 0.32, 4.0, $1.2cmol^+\;kg^{-1}$, respectively. Soil chemical properties was related with topography except soil pH. A soil pH and organic matter, available phosphate, exchangeable potassium increased with time while exchangeable calcium, magnesium available silicate decreased with time.

• Journal of the Korean Chemical Society
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• v.26 no.5
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• pp.333-339
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• 1982

Substituent effects of substrate and leaving group for the reaction of substituted ${\beta}$-phenylethyl arenesulfonates with pyridine were determined conductometrically in acetonitrile at 50∼70$^{\circ}$C. The substituent effect in substrate is not so significant than expected, but still the electron donating substituent shows the slight acceleration to give a small negative ${\rho}$ value and Hammett plots show slight curvature on the acting substituents, even though it is not so remarkable than that of benzyl system. These results represent a little bit the favorable bond breaking at the transition state by the electron donating substituents. The effects of leaving group in the arenesulfonates in which the rate constants are decreased by electron donating substituents, while electron withdrawing groups presented the reverse effects. Hammett ${\rho}$ value is significantly smaller than that of p-nitrobenzyl arenesulfonates and thus, the mechanism should be closer to tight $S_N2$ one. Especially 2,5-dichlorobenzenesulfonate was more accelerated than expected at the additivity of substituents. This facts showed that dichlorobenzenesulfonate anion is more stabilized by the great electron withdrawing substituents at transition state.

• Applied Biological Chemistry
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• v.43 no.1
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• pp.52-56
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• 2000

The influence of the 2-(4-(6-chloro-2-benzoxazolyloxy)phenoxy)-N-phenyl- propionamide derivatives on the herbicide activities against rice plant with pre-emergence and post-emergence in down land were examined and the structure activity relationship (SAR) were analyzed by Free-Wilson and Hansch method. In pre-emergence, the SAR approach is shown that the optimal, $({\pi})_{opt}=0.91$, hydrophobicity with electron donating effect of the ortho substituted mono substituents and 2,3,4-substituted three substituents were found to be contribute the herbicidal activity. Whereas, in post-emergence, the optimal, ({\pi})_{opt}=0.50$, hydrophobicity with electron withdrawing effect of meta substituted mono subsituents and 2,3-substituted two substituents were found to be contribute the herbicide activity. The herbicide activities with post-emergence more increase than that of pre-emergence. It is assumed from the SAR equations that the 2-methyl-3-methoxy-4-cyano group substituent is selected as the most lowest herbicide activity against rice plant with post-emergence in green house. The hydrolysis reaction was proceeded through nucleophilic addition-elimination (Ad_{Nu-E})$ with the orbital control between LUMO of substrate and HOMO of water molecule. And molecular electrostatic potential (MEP) of none (H) substituent was discussed.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.601-613
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• 2007

It is reported that factors affecting the behavior of reinforced earth retaining walls built on soft ground are not only basic physical properties but also the increase of load by the reinforced earth retaining walls, consolidation period, pore water pressure, etc. This study analyzed the behavior of reinforced earth retaining walls and soft ground using SAGE CRISP, a ground analysis program. First, we examined the effect of the replacement method, which was to prevent the excessive displacement of reinforced earth retaining walls, in improving the behavior of the walls. Second, we compared and analyzed how the behavior of ground is affected by the vertical interval of stiffeners on the back of reinforced earth retaining walls after the application of the replacement method. Lastly, we proposed the optimal replacement width and depth in the application of the replacement method. The results of this study proved that the replacement method is considerably effective in improving the behavior of reinforced earth retaining walls. In addition, the vertical interval of stiffeners on the back of reinforced earth retaining walls appeared effective in improving the horizontal displacement of the top of retaining walls but not much effective in improving the vertical displacement of the back of retaining walls. In addition, improvement in horizontal-vertical displacement resulting from the increase in replacement width was not significant and this suggests that the increase of replacement width is not necessary. With regard to an adequate replacement depth, we proposed the ratio of replacement depth to the height of retaining walls(D/H) according to the ratio of the thickness of the soft layer to the height of retaining walls(H/T).

• Clinics in Shoulder and Elbow
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• v.16 no.2
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• pp.163-169
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• 2013

Designs of total elbow arthroplasty have been evolving with clinical experiences. Newer implants are expected to resolve current limitations and improve long term outcomes. This review article focuses on the basic knowledge of unlinked and convertible total elbow arthroplasty. There have been a variety of designs of unlinked total elbow prostheses. Some implants are still used in the market, while others are no longer commercially available. Modified and newer designs include more congruent contact surface, stemmed implant, and radiocapitellar arthroplasty. Two convertible elbow prostheses have been developed, and one implant is currently available in Korea. Conversion from an unlinked to a linked mode is performed by adding a linking cap. Unlinked total elbow arthroplasty, which restores native elbow kinematics, has a biomechanical rationale of lowering polyethylene wear and loosening of implants. It can be indicated in younger and higher demand patients, who have adequate bone stock and soft tissues. Convertible total elbow arthroplasty broadens implant selection and simplifies revision surgery. These newer prostheses possibly improve the long term outcomes and resolve disadvantages of linked prostheses in total elbow arthroplasty.