• Journal of the Korean Institute of Gas
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• v.22 no.5
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• pp.53-61
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• 2018

Low-salinity water based polymerflooding (LSPF) is one of promising enhanced oil recovery (EOR) method that has the synergetic effect of combining polymer injection method and low-salinity water injection method. In order to maximize EOR efficiency, it is essential to design low-salinity water appropriately considering the properties of polymer. In this aspect, the main purpose of this study is to investigate the effect of pH and $SO_4{^{2-}}$ ion which one of PDI (Potential Determining Ion) on oil production when applying LSPF to carbonate oil reservoir. First, the stability and adsorption of polymer molecule were analyzed in different pH of injection water and $SO_4{^{2-}}$ concentration in injection water. As a result, regardless of pH and $SO_4{^{2-}}$ concentration, when $SO_4{^{2-}}$ ion was contained in injection water, the stability of polymer solution was obtained. However, from the result of polymer retention analysis, in neutral state of injection water, since $SO_4{^{2-}}$ interfered the adsorption of polymer, the adsorption thickness of polymer was thinner as $SO_4{^{2-}}$ concentration was higher. On the other hand, when injection water was acidic as pH 4, the amount of polymer adsorption increased with the injection of polymer solution, so the mobility of polymer solution was greatly lowered. From the results of wettability alteration due to low-salinity water effect, in the case of neutral injection water injected, as $SO_4{^{2-}}$ concentration was increased, more oil which attached on rock surface was detached, altering wettability from oil-wet to water-wet. On the other hand, in acidic condition, due to complex effect of rock dissolution and polymer adsorption, wettability of the entire core system was less altered relatively to neutral condition. Therefore, it was evaluated that better EOR efficiency was obtained when injecting low-salinity water based polymer solution containing high concentration of $SO_4{^{2-}}$ with neutral condition, enhancing the oil production up to 12.3% compared to low-salinity water injection method.

• Journal of The Korean Society of Grassland and Forage Science
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• v.19 no.1
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• pp.75-80
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• 1999

A field experiment was carried out to determine the optimum application level of dicamba herbicide for efficient control of Abutilon avicennae in silage corn field. Five treatments of application levels (0 ; control, $0.75{\ell},\;1.0{\ell},\;1.25{\ell}\;and\;1.5{\ell}$) were arranged at National Livestock Research Institute, RDA, Suwon in 1995 and 1996. The hybrid silage corn was P 3352 and dicamba herbicide was applied at 5~6 leaf stage of corn. The growth of corn was poor in control plot, and the days for tasseling and silking were delayed 2~3 days when compared with the plots of herbicide application. The control efficiency of Abutilon avicennae was excellent as 94.7~98.1% in the plots of dicamba application. A slight injury of herbicide was observed at early stage of corn when applied at $1.0{\ell},\;1.25{\ell}\;and\;1.5{\ell}$ of dicamba per ha. Forage dry matter(DM) yield, length and weight of ear in the plots of dicamba treatments were significantly higher than those of control. The DM yield of control(12,070kg/ha) was only 64.2~66.9% of dicamba treatment plot(18,050~18,795kg/ha). However, there was no yield difference among dicamba application level. The percentage of ear to total DM yield was ranged from 53.4 to 56.8%. The nutritive value(crude protein, ADF, NDF, digestibility and TDN) was very similar among all treatments. From the above results, it is recommended that optimum application level of dicamba herbicide was $0.75{\sim}1.0{\ell}/ha$ for efficient control of Abutilon avicennae and for silage corn production without herbicide injury.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.9-19
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• 2008

The purpose of this study was: (1) to compare nanoleakage patterns of a conventional 3-step etch and rinse adhesive system and two experimental hydrophobic adhesive systems and (2) to investigate the change of the nanoleakage patterns after load cycling. Two kinds of hydrophobic experimental adhesives, ethanol containing adhesive (EA) and methanol containing adhesive (MA), were prepared. Thirty extracted human molars were embedded in resin blocks and occlusal thirds of the crowns were removed. The polished dentin surfaces were etched with a 35 % phosphoric acid etching gel and rinsed with water. Scotchbond Multi-Purpose (MP), EA and MA were used for bonding procedure. Z-250 composite resin was built-up on the adhesive-treated surfaces. Five teeth of each dentin adhesive group were subjected to mechanical load cycling. The teeth were sectioned into 2 mm thick slabs and then stained with 50 % ammoniacal silver nitrate. Ten specimens for each group were examined under scanning electron microscope in backscattering electron mode. All photographs were analyzed using image analysis software. Three regions of each specimen were used for evaluation of the silver uptake within the hybrid layer. The area of silver deposition was calculated and expressed in gray value. Data were statistically analyzed by two-way ANOVA and post-hoc testing of multiple comparisons was done with the Scheffe's test. Silver particles were observed in all the groups. However, silver particles were more sparsely distributed in the EA group and the MA group than in the MP group (p < .0001). There were no changes in nanoleakage patterns after load cycling.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.3
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• pp.334-339
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• 1985

A sweet corn hybrid, Honey Bantam, was planted on 24 May, 1984 in a silty clay loam soil to investigate the effects of polyethylene(P.E.) mulch and different levels and placements of Nitrogen(N) on soil properties and sweet corn growth. A split-split plot design with three replications was employed; P.E. mulch and bare soil were main plot, N levele of 8, 12, 16, and 20 kg/10a were subplot, and band and broadcast of fertilizers were sub-subplots. At early growth stage soil temperature under P.E. mulch was higher than that in bare soil by 5-10$^{\circ}C$, but the differences decreased as plant growth advanced. Soil hardness increased with soil depth while P.E. mulch reduced soil hardness probably by holding high soil moisture. Soil pH decreased up to the 6th week after planting and then increased in bare soil, but it contineously decreased up to the 8th weeks under P.E. mulch regardless N levels and placements. Electrical conductivity(EC) of soil increased up to the 6th weeks after planting and then decreased in all treatments except broadcast of fertilizers under P.E. mulch where EC increased contineously. Generally, soil EC under P.E. mulch was higher than that in broadcast. Broadcast of fertilizers did not affect emergence of seedlings in all N levels under P.E. mulch and bare soil, but band of fertilizers at all N levels under P.E. mulch and higher levels of N in bare soil reduced emergence rate significantly. Percent stand was possitively correlated with soil EC and it strongly influenced the number of marketable ears. Plant growth was enhanced and silking date was earlier by 14-19 days under P.E. mulch compared to bare soil probably due to increased soil moisture, reduced soil hardness and higher soil temperature.

• Journal of Food Hygiene and Safety
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• v.20 no.1
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• pp.22-35
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• 2005

A survey was conducted to investigate the perception of food sanitation officers toward the Genetically Modified Foods. They were mainly from Regional Agencies of KFDA, City/Province office, and National quarantine station. Some of them were professors of university and researchers of research institute. Most of respondents had experiences of hearing or reading GM foods (over $95\%$) and over $90\%$ of respondents much needed the label of GM foods. Although some of officers of city/province office and national quarantine station showed less knowledge than other respondent groups, most of respondents had basic knowledge about biology. The frequency of respondents worked over 20 years and worked in the general administration was higher than that of other groups in the question of unsafe of GM foods. The answer frequency of careless treatment of foods was highest in the question of risk factor, and the frequency of GM foods was lowest ($4.4\%$). It was concluded that food sanitation officers had positive opinion about GM foods, but there were some differences in the knowledge among agencies. Therefore, it is necessary more educations and informations are needed for food sanitation officers.

• Journal of The Korean Society of Grassland and Forage Science
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• v.5 no.1
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• pp.62-72
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• 1985

In order to find out the effects of seeding time on growth, dry matter production and nutritive content of Pioneer 931, Pioneer 988 and Piper, this study was carried out on the experimental field of Livestock Experiment Station in 1981-83. Seeding time were 7 with 14-day interval from April 16 to July 9. The results are summarized as follows: 1. It tool about 12 to 13 days from seeding to emergence in case of Mid-April seeding and 7 to 8 days in Late-June. Earlier seeding, more longer growth period from emergence to heading they required. 2. Plant height of Pioneer 931 seeded lately was longer than 4.5 meters in primary growth and Sudangrass was about 2.0 to 2.5 meters. Leaf area was the greatest in Mid-August by early seeding but it was increased until Early-October by late seeding. 3. Sorghum gas brought the highest yield in dry mater and Sudangrass the lowest. In general dry matter yield reduced gradually in response to later seeding but Pioneer 931 has brought more than 10 tons per hecter until Late-June. 4. Relative Growth Rate, Leaf Area Ratio and Leaf Weight of all varieties decreased in accordance with growth development. 5. Crude protein content of leaf was higher than stem and the younger the plants, the more protein they contain. Nitrogen Free Extract was just opposite to crude protein.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.3
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• pp.359-369
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• 2007

This in vitro study was performed to assess the effect of surface sealing on the microleakage of class V composite resin restorations that underwent several aging treatments. Class V cavities were prepared on the buccal surface of 100 sound extracted premolars and restored with a hybrid light-cured composite resin according to the manufacturer's instructions. They were randomly divided into two groups consisting of 50 samples: group I, without surface sealing, and group II, in which margins were etched and surface sealant was applied. After thermocycling, each group was divided into five subgroups, respectively, to represent the five aging treatments: group A = no further treatment (only thermocycling), B = toothbrushing, C = load cycling, D = toothbrushing followed by load cycling, and E = aging treatment in deionized water for six months. Microleakage was assessed by examining the penetration of 2% methylene blue dye. The following results were obtained: 1. At occlusal and cervical margins in groups without surface sealing, there was no significant difference in microleakage after the several aging treatments (p>0.05). 2. The occlusal margins of groups with surface sealing showed no significant differences after the several aging treatments (p>0.05). 3. In the cervical margins of groups with surface sealing, microleakage significantly increased after load cycling or aging in deionized water for six months (p<0.05). 4. The no-further-treatment group and the toothbrushing group with surface sealing showed less microleakage than the corresponding groups without surface sealing (p<0.05). 5. The surface-sealed groups with load cycling or aging in deionized water showed no significant difference in microleakage to the corresponding groups without surface sealing (p>0.05). In conclusion, the results of this study suggest that the surface sealant infiltrating through the gap of the cervical margin exerted a positive effect on microleakage at the initial stage, but the effect was not sufficient to overcome the stress generated by the cuspal flexure during occlusal loading and water absorption.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.145-155
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• 2002

The results of the present feasibility study are summarized as follows, 1. The three unit bridge of knitted material and UD fibre reinforcement has both the rigidity and the strength against a vertical occlusal load of 75N. 2. Stress concentration at the junctional area between the bridge and the abutments, i.e. between the pontic and the knitted caps was observed. In the case of the bridge with reinforcement straps, it was partly shown that the concentration problem could be improved by simply increasing the fillet size at the area. Further refining in the surface of the junctional area will be needed to ensure a further improvement in the stress distribution. This will require some trade off in the level of the stress and the available space. A parametric study will help to decide the appropriate size of the fillet. 3. Design refinement is a must to improve the stress distribution and realize the most favourable shape in terms of fabrication. The current straight bar with a constant cross section area can be redesigned to a tapered shape. The curve from the dental arch should also be placed on the pontic design. In accordance with design refinement, the resistance of the bridge frame to other load cases should be evaluated. 4. Although not included in the present feasibility study, it is estimated that bridges of the anterior teeth can be made strong enough with the knitted material without further reinforcement using unidirectional materials. In this regard, a feasibility study on design concepts and stress analysis for 3, 4, 5 unit bridge is suggested. 5. Two types of bridge were analysed in terms of fatigue. The safe life design concept, i.e. fatigue design concept, looks reasonable for the bridge where if cracks should form and propagate there is virtually nothing a dentist to do. The bridge must be designed so that no crack will be initiated during the life span. In the case of crowns, however, if constructed with composite resin with knitted materials, it might be possible to repair them, which in general is impossible for crowns of PFM or of metal. Therefore for composite resin crowns, a damage tolerance design concept can be applied and reasonably higher operational stresses can be allowed. In this case, of course, a periodic inspection program should be established in parallel. 6. Parts of future works in terms of structural viewpoint which need to be addressed are summarized as the following: 1) To develop processing technology to accommodate design concepts; 2) More realistic modelling of the bridge and analysis-geometry and loading condition. Thickness variation in the knitted material, taper in the pontic, design for anterior tooth bridge, the effect of combined loads, etc, will need to be included; 3) To develop appropriate design concepts and design goals for the fibre composite FPD aiming at taking the best advantage of knitted materials, including the damage tolerance design concept; 4) To develop testing method and perform test such as static ultimate load test, fatigue test, repair test, etc, as necessary.

• Journal of Aquaculture
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• v.1 no.1
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• pp.67-73
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• 1988

A growth experiment of tilapia (offsprings of the hybrid between Oreochromis niloticus and O. mossambicus) under different dissolved oxygen levels in the recirculating water system was conducted at the Fish Culture Experiment Station of the National Fisheries University of Pusan from February 4 to March 5, 1986. Six tanks with a capacity of $1.8m^3$ of water each were used under the same condition of water parameters except for dissolved oxygen levels which were designated to maintain at 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg/$\iota$. Each tank was stocked with 90 kg of fish each averaging 64 to 69 grams. The average water temperature during the course of the experiment was $22.5^{\circ}C$. The results obtained are summarized as follows: The food conversion efficiencies were very good, being 1.05-1.11 at 3.5, 3.0, 2.5 and 2.0 mg/$\iota$ DO levels without any significant differences among them, but at 4.0 mg/$\iota$ the F. C. was 1.39 and at 1.5 mg/$\iota$ it was 1.61 being very poor compared with the others. The daily growth rate performance was best at 3.5 mg/$\iota$ dissolved oxygen level followed by 3.0 and 2.5 mg/$\iota$ with slight differences while at 4.0 and 2.0 mg/$\iota$ DO levels the growths were significantly poor, and at 1.5 mg/$\iota$ DO level it was extremely poor. In 1.5 mg/$\iota$ group, the fish did not accept feed vigorously and after feeding the fish usually concentrated around the inflow point showing oxygen deficiency response. While at 4.0 mg/$\iota$ high feeding rates tended to waste significant amounts of feed while eating and led to water deterioration, and above these levels the results is considered to lead to a waste of energy with uneconomical performance. On the other hand, at and below 2.0 mg/$\iota$ DO level the tilapia certainly showed a poor growth performance. The experiment indicates that the DO range of 2.5$\~$3.5 mg/$\iota$ is the optimum level for the good growth performance.

• KDI Journal of Economic Policy
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• v.13 no.1
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• pp.167-197
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• 1991

This paper is intended as an introductory essay to explain endogenous changes in the scope of firm activities in the competitive structure of a deregulated, multi-product financial industry. Recently, the global financial industry has been experiencing a widespread reshuffling in its activities, reflecting both consolidation and specialization. The spread of the universal banking system, which involves the integration of various kinds of financial activities, has resulted in the so-called financial supermarket. At the same time, the traditional set of banking activities has been unbundled into so-called financial boutiques. A relevant question is where the current reshuffling process of integration and disintegration in financial activities might lead the financial industry. However, presently popular theories of the financial industry are not really appropriate for the analysis of this issue. This paper attempts to integrate the theory of specialization [George J. Stigler, "The Division of Labor is Limited by the Extent of the Market," Journal of Political Economy, Vol. LIX, No.3, June 1951] and the theory of the multi-product firm [William J. Baumol, John C. Panzar, and Robert D. Willig, Contestable Markets and the Theory of Industry Structure, Harcourt Brace Jovanovich, Inc., New York, 1982] and to apply the resulting hybrid theory, a theory on the scope of financial activity, to the financial industry. The implications of this theory for the issues raised above are formalized under five hypotheses on the reshuffling of financial activities as listed below: Hypothesis I: The differences in the organization of financial industries among countries are determined by differences in the size of the financial markets, other things being equal. Hypothesis II: A financial firm will separate those financial activities simultaneously having relatively strong economies of scale and relatively weak economies of scope (alternatively, diseconomies of scope) from other activities. Conversely, the firm will integrate those activities simultaneously having relatively weak economies of scale (alternatively, diseconomies of scale) and relatively strong economies of scope with incumbent activities. Hypothesis III: A competitive equilibrium in the deregulated financial industry will consist of both specialized and multi-product financial firms, resulting in a mixed form of specialized and universal banking systems. Hypothesis IV: As world financial markets fully integrate and all countries consequently face this single, common world market, the financial structures of individual countries will become increasingly similar. Hypothesis V: A more universal banking system will dominate the deregulated financial industry in countries with relatively small financial markets, while a more specialized banking system will dominate in countries with relatively large financial markets. However, equilibrium will ultimately be mixed, with specialized and universal banks coexisting, as stated in Hypothesis III. Based on these hypotheses, this paper interprets the historical development of specialized vs. universal banking systems in major industrial countries as a process driven by the evolution of the financial market in each country - i.e. the change in the size of the financial market over time. In addition, this paper anticipates that the final equilibrium of the world financial industry, which is currently under the pressure of financial innovations and deregulation, will be a mixed equilibrium with both specialized boutiques and universal supermarket-type financial firms, instead of an exclusively specialized or universal banking system. Future research should seek continued theoretical elaboration and empirical verification of this paper's hypotheses.