• Korean Journal of Materials Research
• /
• v.3 no.5
• /
• pp.497-504
• /
• 1993

Effects of $Ta_2O_5,ZrO_2$ and $SiO_2$ addition on magnetic properties of 0.02wt%$Bi_2O_3$ and 0 . 0 5 wt%$CaCO_3$ doped Mn-Zn ferrites(58.5mol% $Fe_2O_3$, 25.5 mol% ZnO) were investigated. E:lectrlcal resistivity and magnetic properties such as the initial permeability($\mu_i$), loss factor(tan$\delta$), coercive force Hc(m0c) were measured. With lncreasing $Ta_2O_5$ and $ZrO_2$ addition, the following effects were observed: I ) Decreasing of the average grain size; 2) lncreasing of the electrical resistivity and initial permeability; 3) Ilecreasmg of loss factor values. (very low loss esprcially at high frequency region) ; 4 ) Fine and uniform microsrructures were obtamed at O.lwt% nddecl samples. In case of $SiO_2$ addition, anomalous grain growth and degradation of magnetic properties were observed. The obtained maximum initial permeability value was 6260 at IOkHz. $25^{\circ}C$ from 0.02wt%$Bi_2O_3$. 0.05wt%$CaCO_3$, 0.lwt%$Ta_2O_5$ added sample, the corresponded relative loss factor (tan$\delta /\mu_i$)for the sample was $4.2 \times 10^{-6}$.

• Management & Information Systems Review
• /
• v.15
• /
• pp.109-145
• /
• 2004

Upcoming 21st century, Management circumstance for a small and medium enterprise have been rapidly changed by Knowledge management, Informationization, Hi-technology. Changing from an era of small concept to strong concept, It will be a severe innovation period and can not survive with life as the same as the past, It is the era of best which mean only the best can survive, None of the average faculty can survive. Due to rapid proceeding of innovation of Informationization, It stimulate acceleration of technology innovation, infinity competition regardless the nation boarder, result in proceeding to Informationization. A small and medium enterprise is defined as smaller size of business than big business as point of capital, employee, output. It is concept, which usually used against concept of big business. When define a small and medium enterprise, criteria to determine a small and medium enterprise is depends on country and a category of business. However, In every country, A small and medium enterprise is getting be bigger and importance factor in whole industry. A small and medium enterprise is well developed and also well balanced with a large enterprise in the developed country. All around in the world, Interest about a small and medium enterprise is becoming higher. It is actively researching into a small and medium enterprise as the mean to create new employment, new industry, as means to from integration of a all and medium enterprise,as source of high competitive power. The status quo of rapid changing into informationization have been realized at considerable level in Korea. Information society is defined as information technology is main key to determine individuals competitiveness, which can solve effectively the side effect result from industrialization. It cleary imply that information technology is the most promising and important industry in 21st century. Therefore, We should seek to foster independent a small and medium enterprise and develop them corresponding to new concept of a small and medium enterprise in 21st century. The main frame of policy should be new economic system, which can contribute establishment of a small and medium enterprise, management innovation. It also attribute a small and medium enterprise to reveal their creative. New economic paradigm in 21st will be expanded with organization, market, technology. So far, a small and medium enterprise has been acknowledge as economic weaker and the one should be protected. However, In 21st century a small and medium enterprise will be considered as active majority or a source of creative. Development of technology to produce a small quantity with variety product and acceleration of knowledge and informationization will result in comparative merits of a small and medium enterprise. Hereby, The role and relative importance of a small and medium enterprise in our economic will getting be larger and It will be developed as the main force to activate the economic. However, Only a small and medium enterprise, which overcome difficulty with active desire and effort to improve their lot can be developed as a competitive enterprise in 21st century in considering themselves to be developed as diversity, active, independent, business by an enterprise.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.44 no.2
• /
• pp.141-149
• /
• 2018

The structure of the coacervate can dramatically influence deposition on the hair. The purpose of this study was to investigate the effect of coacervate with a relatively fine and uniform structure on the surface properties of hair and its influence on hair damage. In this study, coacervates of different sizes were explored in 10% shampoo solutions; one solution contained coacervates with non-uniform sizes ($10-300{\mu}m$ average), and the other solution formed a coacervate with a fine and uniform ($1-3{\mu}m$) structure. To study the effect of shampoo on the physical properties of hair and damage to the hair, the hair breakage characteristics, color changes, friction properties, lipid contents and hair surface were examined after using two different types of shampoo. The results clearly show that the relatively fine and uniformly sized coacervate was evenly deposited over the surface of the hair. As a result, the coacervate system can substantially influence the surface properties of the hair such as hair friction, breakage characteristics, and color. The frictional force was dramatically reduced. The use of a fine and uniformly sized coacervate can notably improve hair surface properties. Consequently, hair breakage decreased, and the effect of the coacervate on hair damage was remarkably high.

• The Journal of Korean Academy of Prosthodontics
• /
• v.41 no.2
• /
• pp.232-242
• /
• 2003

Statement of problem : Fiber-reinforced posts have lower modulus of elasticity than titanium post or cast post-core. With this similar elasticity to that of dentin, fiber-reinforced posts have been known to have a tendency to reduce the risk of root fracture. However, there were few studies on the teeth restored with fiber-reinforced posts under the condition of reduced periodontal support. Purpose : The purpose of this study was to evaluate the fracture strength and failure mode of endodontically treated teeth restored with fiber-reinforced posts and titanium posts under the condition of reduced periodontal support. Material and method : Extracted human maxillary incisor roots were divided into 3 groups (group 1 carbon fiber post, group 2 : glass fiber post, and group 3 : titanium alloy post). After coronectomy and endodontic treatment, teeth were restored with each post systems and resin core according to the manufacturer's recommendation. Then, teeth with simulated periodontal ligament were embedded in the acrylic resin blocks at the level of 4 mm below the cemento-enamel junction. Each specimen was exposed to $10^5$ load cycles with average 30 N force in $36.5^{\circ}C$ water using a computer-controlled chewing simulator. Loads were applied at $45^{\circ}$ angle to the long axis of the teeth. After cyclic loading, teeth were subjected a compressive load until failure at a crosshead speed of 0.5 mm/min. Fracture strength (N) and failure mode were examined. The fracture strength was analyzed with one-way ANOVA and the Scheffe adjustment at the 95% significance level. Results and conclusion : The results were as follows. 1. There was no statistically significant difference in the mean fracture strength among the groups (P<.05). 2. Carbon fiber post and glass fiber post group showed less root fracture tendency than control group. 3. All specimens with root fractures showed fracture lines above the level of acrylic resin block, except for only one specimen in group 3.

• Macromolecular Research
• /
• v.12 no.1
• /
• pp.127-133
• /
• 2004

We have studied the surface micelle formation of polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) at the air-water interface. A series of four PS-b-P2VPs were synthesized by anionic polymerization, keeping the PS block length constant (28 kg/㏖) and varying the P2VP block length (1, 11, 28, or 59 kg/㏖). The surface pressure-area ($\pi$-A) isotherms were measured and the surface morphology was studied by atomic force microscopy (AFM) after Langmuir-Blodgett film deposition onto silicon wafers. At low surface pressure, the hydrophobic PS blocks aggregate to form pancake-like micelle cores and the hydrophilic P2VP block chains spread on the water surface to form a corona-like monolayer. The surface area occupied by a block copolymer is proportional to the molecular weight of the P2VP block and identical to the surface area occupied by a homo-P2VP. It indicates that the entire surface is covered by the P2VP monolayer and the PS micelle cores lie on the P2VP monolayer. As the surface pressure is increased, the $\pi$-A isotherm shows a transition region where the surface pressure does not change much with the film compression. In this transition region, which displays high compressibility, the P2VP blocks restructure from the monolayer and spread at the air-water interface. After the transition, the Langmuir film becomes much less compressible. In this high-surface-pressure regime, the PS cores cover practically the entire surface area, as observed by AFM and the limiting area of the film. All the diblock copolymers formed circular micelles, except for the block copolymer having a very short P2VP block (1 kg/㏖), which formed large, non-uniform PS aggregates. By mixing with the block copolymer having a longer P2VP block (11 kg/㏖), we observed rod-shaped micelles, which indicates that the morphology of the surfaces micelles can be controlled by adjusting the average composition of block copolymers.

• Journal of Wetlands Research
• /
• v.11 no.1
• /
• pp.115-121
• /
• 2009

The hybrid constructed wetland(HCW) as tertiary treatment process of a bio industrial wastewater treatment plant was employed to estimate applications for the reuse of final effluent. Raw wastewater was sequently treated through chemical and biological treatment processes and the biologically treated water was flowed into the HCW. The HCW system was composed of two constructed wetlands connected in series; The one is the aerobic constructed wetland with natural air draft system whose driving force for air supply was the difference between the temperature of the air inside the wetland and the ambient air, and the other is the anaerobic/anoxic constructed wetland. Average influent concentrations of BOD, SS, T-N and T-P in the HCW were 53mg/L, 48mg/L, 34mg/L and 3mg/L, respectively. After being treated at HCW, final effluent concentrations of BOD, SS, T-N and T-P were 2.3mg/L, 1.2mg/L, 7.95mg/L and 0.83mg/L, respectively. Referring to a reuse standard for a sewage wastewater, final effluent could sufficiently be reuse as landscaping, washing or agriculture water. HCW system with the aerobic/anaerobic combined constructed wetland could be achieved a high removal efficiency because each constructed wetland was functionalized to be removed efficiently organics, nitrogen and phosphorus. HCW system could be estimated to be successful application as tertiary treatment process of a various industrial and municipal wastewater.

• Journal of Environmental Policy
• /
• v.4 no.1
• /
• pp.1-19
• /
• 2005

On January 1, 2005, the Special Act on Metropolitan Air Quality Improvement, known as the Blue Sky 21 Program, entered into force. This Special Act is aimed at reducing the annual average concentrations of $PM_{10}$ and $NO_2$ to $40{\mu}g/m^3$ and 22ppb, respectively, from their current levels of $76{\mu}g/m^3$ and 36ppb, within the next 10 years. While the main focus of the Act is to reduce $PM_{10}$ and $NO_2$ emissions, the government also anticipates that these reductions would lessen high ozone occurrences and improve visibility. However, reducing local PM emissions would not decrease $PM_{10}$ concentrations as much as expected since other significant sources, such as continental inflow and/or secondary formation from photochemical reactions, exist. This is corroborated by the fact that $PM_{10}$ in the greater Seoul Metropolitan area during the ozone season is mostly in the form of $PM_{2.5}$, which is secondarily formed on a regional scale. Furthermore, many modeling results indicate so-called '$NO_x$ disbenefits,' referring to the fostering of an increase in ozone concentrations from a decrease in $NO_x$ emissions, over an extensive area. In this paper, the current status of air quality in the Seoul Metropolitan area is reviewed, and several other issues, including the effect of long-range transport, photochemical characteristics, and tasks for successful implementation of the Special Act are discussed.

• Journal of Family Resource Management and Policy Review
• /
• v.10 no.3
• /
• pp.131-148
• /
• 2006

The purpose of this study is to examine the allocation of time between work and leisure by the rural elderly in Korea. The data used for this study are collected from fm households during the peak ($17^{th}\;to\;30^{th}$ June) and off-peak ($28^{th}$ November to $10^{th}$ December) farming seasons of 2005 using time diary. The sample for this study consists of 120 elderly over 65 years old living in rural area in eight provinces. The major findings are as follows. (1) The time spent of farm work by rural elderly in much longer than average work hours of elderly in general regardless of farming season. The indicates that the elderly farmers are the sustaining forces of agriculture as the urban industrial sector absorbs the younger labor force rural area. (2) There are significant differences in the work time(including form work, housework, and farm work plus house work) by gender, age, education, marital status, living arrangements. (3) The rural elderly spends less time in leisure compared to the elderly in general even during the off-peak season. (4) Especially during the peak season, time allocation between work and leisure by the rural elderly is heavily skewed, resulting in an inadequate amount of time for reproduction of labor. (5) There is only significant age difference in the amount leisure time regardless of farming season. (6) Male elderly farmers work approximately 30 minutes to 1 hour longer on farm than the females do, but the total work time (farm work plus housework) of female elderly is longer than that of the male elderly. There is no significant gender difference in the amount of leisure time during the peak season, whereas the men have more leisure than the women during the off-peak season. To conclude, the gender differences in time allocation among the rural elderly are minimal. However, the rural elderly of both genders suffers from excessive work hours and heavy workload compared to the urban counterpart.

• Proceedings of the KSEEG Conference
• /
• 2002.10a
• /
• pp.53-67
• /
• 2002

As in the past, we are concerned today with the magnitudes of mineral resources and the adequacy of these resources to meet future needs. In looking at global resource issues, we should consider the need for the resource, its supply, and the environmental consequences of using it. The need for a resource can become a resource dependency, specially as the global population expands and each of us becomes Increasingly dependent upon hundreds of natural materials. Therefore, our great mineral consumption makes the human population a true “Geologic Force”, which will be even more significant in the future when the global population is projected to reach alarming proportions. Although our supplies of mineral resources probably will be sufficient for the 21st century, the uneven distribution of minerals in the Earth's crust almost certainly will continue to be a major problem. The most likely result will be major shifts in both prices and sources of supply of many mineral resources. As for energy resources, we must avoid an obsessive dependency on one fuel and expand instead to other energy resources. Finally, because the use of resources affects the environment, we need to focus on resource exploitation and global pollution, particularly in regard to ground water and arable land. We must manage our resources so as to be in balance with our environment. And the accelerated industrialization of South Korean economy over the last three decades has resulted in the mass consumption of mineral commodities. South Korea has around 50 useful mineral commodities for the mineral industry, among 330 kinds of minerals described. The component ratio of the mining industry sector of the gross national production(GNP) in South Korea dropped from 1.2% in 1971 to 0.34% in 1997 due to the rapid growth of other industries in the country. During the period from 1971 to 1997, the average growth rate of mineral consumption in South Korea was 9.13% yearly and that of GMP per capita was 14.97%. The mineral consumptions per capita showed a continual increase during the last 30 years as follows(parenthesis: GW per capita); 0.99 metric tons in 1997($289), 3.83 metric tons in 1989($5, 210), 6.11 metric tons in 1995 ($10, 037), and 6.66 metric tons in 1997($9, 511). The total amount of mineral consumption in South Korea was 33 million tons of 32 mineral commodities in 1971, and 306 million metric tons of 47 mineral commodities in 1997.

• Journal of Animal Science and Technology
• /
• v.49 no.4
• /
• pp.509-514
• /
• 2007

This study was conducted to investigate the optimal energy level at growing Korean black goat from April 20 to November 6, 2006. Forty male Korean black goat were divided into four treatments and were fed with concentrate feed containing ME 2.4, 2.6, 2.8 and 3.0 Mcal/kg with CP 15% and rice straw. Average daily gains of were 59.8, 65.4, 73.2 and 77.2 g/day in groups fed with ME 2.4, 2.6, 2.8 and 3.0 Mcal/kg diet, respectively. There was a tendency to increase ADG as the ME level of concentrate feed grew. Dressing percentage were 49.73, 48.64, 50.19 and 51.36% in each group, and were increased as the ME level grew. Meat percentage ranged between 53.1 and 55.3%, and were almost constant. Ranges of crude fat contents and water holding capacity were and 57.9~59.0%, which were increased as the ME level grew. On the other hand, shear force were between 2.8 and 3.1 kg/cm2, which were decreased as the ME level grew. These results suggest that the optimal energy level at growing goat's concentrate is ME 3.0 Mcal/kg.