• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.502-509
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• 2001

In this paper, when stress waves are propagated along the reinforced direction of the composite, the characteristic equation of Rayleigh wave is derived. The relationships between velocities of stress waves and Rayleigh wave are studied for anisotropic ratios(E(sub)11/E(sub)12 or E(sub)22/E(sub)11). The increments of anisotropic ratios is made by using known material properties and being constant of basic properties. When the anisotropic ratios are increased, Rayleigh wave velocities to the shear wave velocities are almost equal to 1 with any anisotropic ratios. Rayleigh wave velocities to the longitudinal wave velocities and Shear wave velocities ratio to the longitudinal wave velocities are almost identical each other, they are between 0.12 and 0.21. When the anisotropic ration is very high, that is, E(sub)11/E(sub)22=46.88, Rayleigh wave velocities and the shear wave velocities are almost constant with Poissons ratio, longitudinal wave velocities are very slowly increased with the increments of Poissons ratios. When E(sub)11(elastic modulus of the reinforced direction)and ν(sub)12 are constant, Rayleigh wave velocities and the shear wave velocities are steeply decreased with the increments of anisotropic ratios and the velocities of longitudinal wave are almost constant with them. When E(sub)22(elastic modulus of the normal direction to the fiber) and ν(sub)12 are constant, Rayeigh wave velocities is slowly increased with the increments of anisotropic ratios, the shear wave velocities are almost constant with them, the longitudinal wave velocities are steeply increased with them.

• The Journal of the Korean Society for Microbiology
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• v.18 no.1
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• pp.53-58
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• 1983

Enterotoxigenic E. coli is one of causative agents of the infantile diarrhea and traveler's diarrhea. A modified infant mouse assay(IMA) was developed for the detection of heat stable enterotoxin (ST) of E. coli isolated from diarrheal and control infants and assay system was established with using enterotoxin producing reference strains. The supernatant of the 24 hour-shaking culture of E. coli in Casamino Acid Yeast Extract Salt Broth(CYES-2) was ingested orally into the 2-4 day old ICR mice. After the mice were kept at $25^{\circ}C$ for 4 hours, they were sacrificed and the gut weight body weight ratio(GW/BW) was taken as the index of fluid accumulation induced by heat stable enterotoxin of E. coli. The results obtained were as follows; 1. The GW/BW responses of IMA tested with enterotoxin reference strains of E. coli(E. coli O148H28:$ST^+LT^+$, E. coli $O78H^-:ST^+LT^+$, E. coli O15H11:$ST^-LT^+$, E. coli O1H7:$ST^-LT^-$) appeared ta be ST dose-dependent, and not LT-dependent. From the dose-response curve, $25{\mu}l$ of culture supernatant was determined as test amount of the IMA. 2. Frequency distribution of IMA result from 643 strain of E. coli showed normal distribution at low GW/BW ratio and dispersed pattern at high GW/BW ratio. The GW/BW ratios of $0.056{\pm}0.004(mean{\pm}SD)$ of normal distribution which distributed from 0.044 to 0.068(P<0.01) was considered as ST negative. Thus the GW/BW ratio above 0.069 could be regarded as ST positive.

• Journal of Nutrition and Health
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• v.31 no.8
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• pp.1254-1262
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• 1998

This study has done to investigate the relationship between the icreased lipid oncentration caused by smoking and plama levels of vitamin A and vitamin E, antiodative enzyme activity, and lipid peroxidation , in 52 male smokers and 32 non-smokers, Dietary vitamin A and vitamin E intake was imilar in both smokers and non-smokers. Absolute plasma concentrations of vitamin A and vitamin E were not significantly different between two groups, whereas vitamin E/cholesterol ration in plasma was low or in smokers than in that of non-smokers(p<0.05). It was considered that this lowered effect was due to the elevated plasma lipid concentration rather than oxidant stress derived from smoking, in view of the fact that smokers had higher cholesterol (15.2%) adn LDL-C(26.6%) levels than non-smokers. In non-smokers, plasma thiobarbiturin acid reactive substances(TBARS) conrrelated positively with total cholesterol(r=0.63466, p<0.001), LDL-C level(r=0.57166, p<0.01) , and LDL-C/HDL-C ratio(r=0.45926, p<0.05) . Activities of glutathione perosidase(GSH-Px) , superoside dismutase(SOD), and catalse made no difference in both groups. However, it was observed in non-smokers that GSH-Px activity had negative correlations with total cholesterol(r=-0.67293, p<0.001), LDL-C level(r=-0.62878, p<0.001), and LDL-C/HDL-C ratio (r=-0.58824, p<0.01), indicating that there was a dependent relationship between lipid perosidation and plasma lipid level. The smokers also showed negative correlations for GSH-Px activity with total cholesterol (r=-0.29946, p<0.05) and LDL-c level (r=0.45914, p<0.001), and LDL-C/HDL-c ratio(r=-0.35438, p<0.05). It seemed that the lipid that the lipid level elevated by sustaines smoking resulted in reducing vitamin E/cholesterol ratio and proportion of antioxidant to oxidant load, and then GSH-Px activity, with insufficient removal of free radicals(TBARS 2.43$\pm$0.51 and 1.81$\pm$0.15nmol/ml in smokers and non-smokers, respectively). These findings suggest that higher plasma lipid levels may play a more important role in perturbing the antioxidant defense system including vitamin E status and GSH-Px activity, at least in circumstances that increase lipid concentration . In addition, in exposure to free radicals like those in cigarette smoke. In those cases the ratio of vitamin E/lipid in plasma can be a more indicator of vitamin E status than plasma levels of vitamin E alone.

• Journal of Korea Water Resources Association
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• v.44 no.8
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• pp.683-694
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• 2011

To analyze the regional impact of air temperature increase and precipitation variation on water resources, the variability of precipitation-effectiveness (P-E) ratio which is estimated using precipitation and air temperature data of 59 weather stations operated by the Korean Meteorological Administration (KMA) during 1973~2009 was analyzed. Also runoff data resulting from the Precipitation-Runoff Modelling System (PRMS) modelling were analyzed during 1966~2007. The overall spatio-temporal variability of P-E ratio and runoff data in South Korea is corresponding to the variability of precipitation amount. However some region shows that the P-E ratio decreases even though the trend of precipitation amount increases which may be caused by the air temperature increase. Runoff trend is similar to that of P-E ratio. Precipitation and P-E ratio have decreased all seasons except summer season and it means the reduction of available water resources during those seasons. These variability should be reflected in the spring, fall, and winter water supply strategy.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.647-654
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• 2000

During consolidation, the permeability of clay decreases with void ratio because of the reduction in total void space. After Kozeny(1927) and Carman(1956), many researchers have proposed the relations between void ratio and permeability. Most of the relations are expressed in the following forms as : (1) log e - log k(1+e), (2) e - log k, or (3) log e - log k. These relations have been found valid for a large number of normally consolidated clays. From laboratory test(CRS and I $L_{CON}$) results, the relation between void ratio and permeability of Kimhae clay was well defined in all of the three forms. Permeability change index, $C_{k}$, of Kimhae clay was in the range of 0.64~1,03 and average value of $C_{k}$ was 0.821. And the test results satisfied the experimental correlation between $C_{k}$ and e, $C_{k}$=0.5e. In log e - log k(1+e) relation, constant C was in the range of 1.91~4.74$\times$10$^{-8}$ cm/sec and n was in the range of 3.74~4.60.c and n was in the range of 3.74~4.60.74~4.60.0.

• Journal of the Korea Safety Management & Science
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• v.4 no.4
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• pp.109-118
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• 2002

Such effects would be paid off in the right way only when management of the firms perform marketing activities focusing on long term effectiveness, which would drive company profits up and keep them for long. Demands of customers are being changed and varied. In this result with the advantage of mass marketing and database marketing have been drawing attentions from company. To fulfill these demands of customer, they need a concept of eCRM(Web based Customer Relationship Management), and go from selling products and services, or gathering customer requests, up to the phase of solving customer's problem by real time or previous action. With the help of internet, the frequency and speed of the problem solving has improved greatly. For these purposes, we try to determine the most important and most urgent factors in eCRM: utilization by using SN Ratio Decision making, one of the Multi-criteria decision-making methods SN Ratio Decision making is widely used for determining relative magnitude per evaluation item, i. e. priority on problems and is expected to make more systematic and objective evaluations than conventional methods do. Even in the present situation where any general criterion on eCRM dose not exist, utilization of eCRM is expected to be actively continued, which will cause many problems. In this regard, evaluating eCRM counts.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.669-678
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• 2009

The reduction of excess activated sludge from petrochemical plant was investigated by the electro fenton (E-Fenton) process using electrogenerated hydroxyl radicals which lead to mineralization of activated sludge to $CO_2$, water and inorganic ions. Factors affecting the disintegration efficiency of excess activated sludge in E-Fenton process were examined in terms of five criteria: pH, $H_2O_2/Fe^{2+}$ molar ratio, current density, initial MLSS (mixed liquid suspended solids) concentration, $H_2O_2$ feeding mode. TSS total suspended solid and $TCOD_{cr}$ reduction rate increased with the increasing $H_2O_2/Fe^{2+}$ molar ratio and current density until 42 and $6.7 mA/cm^2$, respectively but further increase of $H_2O_2/Fe^{2+}$ molar ratio and current density would reduce the reduction rate. On the other hand, as expected, increasing pH and initial MLSS concentration of activated sludge decreas TSS and $TCOD_{cr}$ reduction rate. The E-Fenton process was gradually increased during first 30 minutes and then linearly proceed till 120 minutes. The optimal E-Fenton condition showed TSS reduction rate of 62~63% and $TCOD_{cr}$ (total chemical oxygen demand) reduction rate of 55~56%. Molar ratio $H_2O_2/Fe^{2+} = 42$ was determined as optimal E-Fenton condition with initial $Fe^{2+}$ dose of 5.4 mM and current density of $6.7{\sim}13.3 mA/cm^2$, initial MLSS of 7,600 mg/L and pH 2 were chosen as the most efficient E-Fenton condition.

• Industrial Engineering and Management Systems
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• v.14 no.2
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• pp.111-121
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• 2015

A correct information of customer returns ratio under e-commerce is not always shared between supply chain (SC) members. Also, it is important issue for SC members to handle the unsold products in a market. This paper discusses the impact of information sharing of customer returns ratio on an optimal sales strategy including resale of customer returns and buyback policy for a SC under e-commerce with a manufacturer and a retailer. A retailer sells a single product and resells the resalable customer returns in the same market. A manufacturer produces the products and buys back the unsold products as to their quality from the retailer. The integrated SC (ISC) determines the optimal product order quantity to maximize the expected profit of the whole SC. The decentralized SC (DSC) makes the optimal decisions for order quantity and the wholesale price of products to maximize the expected profit of each SC member. The effect of information sharing is discussed between SC members under ISC and DSC. The analysis numerically investigates how information sharing of the returns ratio affects the optimal decision and the expected profits under ISC and DSC. Besides, effect of SC coordination to encourage the shift to ISC is discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.87-98
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• 1995

When the crack in orthotropic material is propagating under dynamic model I load, influences of anisotropic property ratio $E_{L}$/ $E_{T}$ on stress and displacement around propagating crack tip are studied in this paper. When M<0.55 and .alpha.=90.deg.(.alpha.; the angle of fiber direction with crack propagating direction, M; crack propagation velocity/shear stress wave velocity), the influence of $E_{L}$/ $E_{T}$ on stress .sigma.$_{x}$, .sigma.$_{y}$, .tau.$_{xy}$ and .sigma.$_{\theta}$ is the greast on .sigma.$_{y}$. Except M<0.55 and .alpha.=90.deg., it is the greast on .sigma.$_{x}$ in any situation. Increasing $E_{L}$/ $E_{T}$, stress components are increased or decreased. When maximum stress is based, the stress .sigma.$_{x}$(.alpha.=90.deg.), .sigma.$_{y}$(.alpha.=0.deg.) and .tau.$_{xy}$ (.alpha.=90.deg.) are decreased with increment of $E_{L}$/ $E_{T}$ in M=0. any stresses except .sigma.$_{*}$x/(.alpha.=0.deg.) are decreased with increment of $E_{L}$/ $E_{T}$ in M=0.9. When .alpha.=90.deg., the influence of $E_{L}$/ $E_{T}$ on displacement U and V is V>U in any velocities of crack propagation, when .alpha.=0.deg., it is VU in M>0.75 and when $E_{L}$/ $E_{T}$ is increased, U and V are decreased in any conditions.sed in any conditions.tions.tions.tions.