• Journal of Pharmaceutical Investigation
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• v.29 no.3
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• pp.193-203
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• 1999

In order to investigate systematically the steady shear flow properties of aqueous po1y(ethylene oxide) (PEO) solutions having various molecular weights and concentrations, the steady flow viscosity has been measured with a Rheometrics Fluids Spectrometer (RFS II) over a wide range of shear rates. The effects of shear rate, concentration, and molecular weight on the steady shear flow properties were reported in detail from the experimentally measured data, and then the results were interpreted using the concept of a material characteristic time. In addition, some flow models describing the non-Newtonian behavior (shear-thinning characteristics) of polymeric liquids were employed to make a quantitative evaluation of the steady flow behavior, and the applicability of these models was examined by calculating the various material parameters. Main results obtained from this study can be summarized as follows: (1) At low shear rates, aqueous PEO solutions show a Newtonian viscous behavior which is independent of shear rate. At shear rate region higher than a critical shear rate, however, they exhibit a shear-thinning behavior, demonstrating a decrease in steady flow viscosity with increasing shear rate. (2) As an increase in concentration and/or molecular weight, the zero-shear viscosity is increased while the Newtonian viscous region becomes narrower. Moreover, the critical shear rate at which the transition from the Newtonian to shear-thinning behavior occurs is decreased, and the shear-thinning nature becomes more remarkable. (3) Aqueous PEO solutions show a Newtonian viscous behavior at shear rate range lower than the inverse value of a characteristic time $1/{\lambda}_E$, while they exhibit a shear-thinning behavior at shear rate range higher than $1/{\lambda}_E$. For aqueous PEO solutions having a broad molecular weight distribution, the inverse value of a characteristic time is not quantitatively equivalent to the critical shear rate, but the power-law relationship holds between the two quantities. (4) The Cross, Carreau, and Carreau-Yasuda models are all applicable to describe the steady flow behavior of aqueous PEO solutions. Among these models, the Carreau-Yasuda model has the best validity.

• Journal of the Korean association of regional geographers
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• v.3 no.1
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• pp.35-50
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• 1997

The purpose of this research seeks to analyze the spatial variations in the sex age structure which have been shown to exist within the study atrea, the Kyonggi province in Korea. In this study it is desired to use the Age Structure Index developed by Coulson in order to describe thi sex age structure of each of 186 tracts that comprise the tracted portion of the Kyonggi province. The mechanics of computing the Age Structure Index are found in the equation describing a linear least squares trend line: y=a+bx. For each census tract, the percentage of the population in each age group(y) was plotted against the middle age of each age group(x). The a is a constant representing the value of y, when x equals zero. The b is the regression coefficient and is a measure of the angle of the slope of the least squares trend line. Thus the value of b is the Age Structure Index for each census tract. The major results of this investigation can be summarized as follows: The spatial distributions of sex age structures in the Kyonggi province are far from random. They have exhibited great regularity with the yonger sex age structures near Seoul and a sharp decline to the older sex age structures out in all derections towards rural region. The results of this investigation should have important general significance for the study of the Kyonggi province Age Structure Index is a flexible, operational definition shich allows sex age structure to be measured, mapped, and incorporated in a wide variety of methods of statistical analysis. Futurer, it has been demonstrated that sex age structure varies spatially within Seoul metropolitan finge and that this variation is relagfed to many other attributes of the population. Especially, Age Structure Index is strongly related to the variables-rate of population growth rate. density, rate of numbers of manufacturing, land price. At the same time, considerably more research is needed before a genmeral body of knowlege concerning sex age structure can be developed.

• Journal of Energy Engineering
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• v.24 no.1
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• pp.32-41
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• 2015

The Metropolitan Area Green Heat Project (MAGHP), which collects unused heat gathered from power plants, steel works, landfills in western Metropolitan area and distribute it to integrated energy business (IEB) companies, is proposed for the purpose of enhancing energy efficiency and providing low-price heat for IEB companies. Therefore, in order to decide on whether to initiate the MAGHP, the economic feasibility analysis of the project is widely demanded. This paper attempts to consider and measure four economic benefits: heat supply benefit, production cost reduction benefit, greenhouse gas mitigation benefit, and air quality improvement benefit. In addition, the paper tries to conduct the economic feasibility analysis. The project requires three-year investment and thirty-year operation. Three important findings emerge from the analysis. First, its net present value is computed to be 1,269 billion won and more than zero. Second, its benefit/cost ratio is calculated to be 1.72 and bigger than 1.0. Third, its internal rate of return is estimated to be 24.26% and larger than the social rate of return, 5.5%. In conclusion, the MAGHP is socially profitable and should be conducted immediately.

• Journal of Animal Science and Technology
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• v.57 no.2
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• pp.5.1-5.8
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• 2015

Background: Korean native chicken (KNC) is a well-known breed due to its superior meat taste. This breed, however, owing to a low growth rate, has a high market price. In order to overcome this disadvantage, the National Institute of Animal Science (NIAS) in Korea developed a commercial KNC breed, named Woorimatdag version 2 (WM2), an upgraded version of the Woorimatdag (WM1) breed and the WM2 was created by crossing the KNC with meat type breeds. This study aims to discriminate between WM2 and other chicken breeds using microsatellite (MS) markers. Methods: A total of 302 individuals from eight Korean chicken populations were examined. The genetic diversity and population structure analysis were investigated using Cervus, API-CALC, STRUCTURE, PowerMarker programs. Results: Based on heterozygosity and polymorphic information content (PIC) values, 30 MS markers were initially selected from 150 markers. The identified average number of alleles (Na), expected heterozygosity, and PIC values for the WM2 samples were 7.17, 0.741, and 0.682, respectively. Additionally, the paternity of individuals was assigned with a success rate of greater than 99% using 12 markers, the best minimum number of markers. The 12 selected markers contained heterozygosity and PIC values above 0.7 and probability of identity values around zero. Using these markers, the determined probability of identity (PI), $PI_{half-sibs}$, and $PI_{sibs}$ values were 3.23E-33, 5.03E-22, and 8.61E-08, respectively. Conclusions: WM2 is well differentiated with respect to other chicken breeds based on estimated genetic distances. The results presented here will contribute to the identification of commercial WM2 chicken in the market.

• Resources Recycling
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• v.18 no.2
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• pp.39-50
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• 2009

Portland cement production is under critical review due to high amount of $CO_2$ gas released to the atmosphere. Attempts to increase the utilization of fly ash, a by-products from thermal power plant to partially replace the cement in concrete are gathering momentum. But most of fly ash is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. Instead, the source of material such as fly ash, that are rich in Silicon(Si) and Aluminium(Al), are activated by alkaline liquids to produce the binder. Hence concrete with no cement is effective in the reduction of $CO_2$ gas. In this study, we investigated the influence of the compressive strength of mortar on alkaline activator and curing condition in order to develop cementless fly ash based alkali-activated concrete. In view of the results, we found out that it was possible for us to make alkali-activated mortar with 70MPa at the age of 28days by using alkaline activator manufactured as 1:1 the mass ratio of 9M NaOH and sodium silicate and applying the atmospheric curing after high temperature at $60^{\circ}C$ for 48hours.

• Polymer(Korea)
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• v.29 no.5
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• pp.468-474
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• 2005

PLGA and PCL copolymers initiated by carbitol as drug carriers were synthesized by ring-opening polymerization of L-lactide (LA), glycolide (GA), and $\varepsilon-caprolactone(\varepsilon-CL)$. Implantable wafers were simply fabricated by direct compression method after physical mixing of copolymers and bovine serum albumin-fluorescein isothiocyanate (BSA-FITC) as a model protein drug. The release amounts of BSA-FITC from wafers were determined by fluorescence intensity using the fluorescence spectrophotometer. Also, the release behavior of BSA-FITC on wafers was controlled by adding the additives such as collagen, small intestinal submucosa (SIS), poly(vinyl pyrrolidone) (PVP), and poly(thylene glycol) (PEG). The wafer prepared by PLGA and PCL exhibited slow release within $10\%$ for 30 days. But, those prepared by a variety of additives exhibited the controlled BSA release patterns with a dependence on the additive contents. furthermore, the wafers containing natural materials such as collagen and SIS showed more zero-order release profile than that with synthetic materials such as PVP and PEG. It was confirmed that the release of BSA from implantable wafers could be easily controlled by adding natural additives.

• Korea journal of population studies
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• v.32 no.1
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• pp.139-164
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• 2009

The first demographic transition refers to the historical decline in mortality and fertility, as shown from the 18th Century in several European populations, and continuing present in most developing countries. The end point of the first demographic transition(FDT) was supposed to be a stationary and stable population corresponding with replacement fertility and zero population growth. In addition, households in all parts of the world would converge toward the nuclear and conjugal types, composed of married couples and their offspring. The second demographic transition(SDT), on the other hand, sees no such equilibrium as the end-point. Rather, new developments bring sub-replacement fertility, a multitude of living arrangements other than marriage, and the disconnection between marriage and procreation. Populations would face declining sizes if not complemented by new migrants. Over the last decades birth rates have been on the decline in all countries of the world, and it is estimated that already more than half of he world's population has below replacement level fertility. Measured in terms of the Total Fertility Rate (TFR), currently 34 countries have fertility levels of 1.5 or less. Similarly, Korea has been below lowest-low fertility for eight consecutive years since 2001 and below the replacement level for more than twenty years. In explaining the low fertility in Korea, some researchers explain the low fertility as revenge against a male-dominated society and institution, while others focus the impact of the employment instability. These studies share the basic ideas (spread of individualism, delayed marriage and childbearing, high divorce rate etc.) of a second demographic transition in order to explain the low fertility in Korea.

• Journal of Gifted/Talented Education
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• v.10 no.2
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• pp.25-46
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• 2000

These purposes are to have a necessity to be educated for the linguistic gifted among many gifted in speedy changeable age, and to find out what differences are of properties between the linguistic gifted children and nongifted children through comparing/analysing to gifted children any nongifted children using performance evaluation on writer's ability. Therefore, it intends to use as a assisting material in order to develop ability and properties of the linguistic gifted children and nongifted children as well. The studying details are 1) to compare/analyze thinking ability between the linguistic gifted children and nongifted children 2) to find out differences of thinking ability for unrealistic reasoning between the linguistic gifted children and nongifted children. The studying subjects had been chosen 3 children as a first grade in 'C' Gifted Academy and 3 children as a first grade in an elementary school from June 3, 1999 to June 12, 1999. The studying instrument was an evaluation of linguistic properties certification(Project Spectrum : Krechevsky,'1994). It had got a frequency calculation, average and standard deviation through the material anylzing with the program SPSSWIN. The conclusions are as belows, First, as a result of performance evaluation on writer's ability to gifted children and nongifted children, the gifted children were outstandingly shown the linguistic ability getting much higher score than nongifted children in respect of vocabulary level, structure of writing, and consistency/logicality of theme. Second, it was shown the gifted children had diffusing thought than nongifted children through the esthetic question and impformation memories with listening to the realistic juvenil story and the unrealistic juvenile story.

• The Korean Journal of Urological Oncology
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• 제15권3호
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• pp.178-186
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• 2017

Purpose: Poloxamer 407 (P407) thermo-sensitive hydrogel formulations were developed to enhance the retention time in the urinary bladder after intravesical instillation. Materials and Methods: P407 hydrogels (P407Gels) containing 0.2 w/w% fluorescein isothiocyanate dextran (FD, MW 4 kDa) as a fluorescent probe were prepared by the cold method with different concentrations of the polymer (20, 25, and 30 w/w%). The gel-forming capacities were characterized in terms of gelation temperature (G-Temp), gelation time (G-Time), and gel duration (G-Dur). Homogenous dispersion of the probe throughout the hydrogel was observed by using fluorescence microscopy. The in vitro bladder simulation model was established to evaluate the retention and drug release properties. P407Gels in the solution state were administered to nude mice via urinary instillation, and the in vivo retention behavior of P407Gels was visualized by using an in vivo imaging system (IVIS). Results: P407Gels showed a thermo-reversible phase transition at $4^{\circ}C$ (refrigerated; sol) and $37^{\circ}C$ (body temperature; gel). The G-Temp, G-Time, and G-Dur of FD-free P407Gels were approximately $10^{\circ}C-20^{\circ}C$, 12-30 seconds, and 12-35 hours, respectively, and were not altered by the addition of FD. Fluorescence imaging showed that FD was spread homogenously in the gelled P407 solution. In a bladder simulation model, even after repeated periodic filling-emptying cycles, the hydrogel formulation displayed excellent retention with continuous release of the probe over 8 hours. The FD release from P407Gels and the erosion of the gel, both of which followed zero-order kinetics, had a linear relationship ($r^2=0.988$). IVIS demonstrated that the intravesical retention time of P407Gels was over 4 hours, which was longer than that of the FD solution (<1 hour), even though periodic urination occurred in the mice. Conclusions: FD release from P407Gels was erosion-controlled. P407Gels represent a promising system to enhance intravesical retention with extended drug delivery.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.1
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• pp.65-75
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• 2019

The government is promoting recycling of waste resources through the enactment of Fundamental Law on Resource Circulation, the revision of the Wastes Control Act and zero-landfilling of untreated waste through improved processes such as recycling and diversification. As of 2015, the total amount of landfilled waste is 38,308 ton/day in Korea. The amount of landfilled waste from industrial sectors is 23,577 ton/day, accounting for 62 % of total landfilled waste. In the study, we investigated the characteristics of the thermal treatment residue among inorganic wastes and estimated the landfill reduction potential according to the relevant recycling criteria, which can go through recycling paths. As a result, it is estimated that about 5~42 % of the landfilled waste can be reduced in case mandatory recycling and landfill suppression policies such as recycling criteria for thermal processing residues and expansion of recycling obligation targets should be implemented. In order to minimize landfill disposal, it is necessary to expand the diversity of waste recycling type and the usage of recycled products.